MvM's hell mode: Guide, tips and tricks to beat wave 666!

Hi! Welcome to my guide on Mann vs Machine's hellish wave 666 a.k.a Nightmare mode. Here i'll go over the basics of each class and their respective roles on this particular mission.

666 is often played by a lot of new people because it gives the most start-up money, which tends to makes them feel a little too confident resulting in a quick defeat by the time the soldier/heavy part of the wave comes. The rules on this mission play differently from standard mvm so i'll hope to cover how to properly beat this and what mechanics lie in this mission.

This is my first guide ever as well but i'll try my best to make the info worth the read! (and good lord is this gonna be a long read)

Feel free to correct me about grammar since english isn't my first language, and when it comes to the information itself correct me too if you want and if it is good enough i'll tweak the guide to add/fix it.

Tricks, Money and 1st half of the wave

TRICKS

One thing to have in mind about this wave is that since everything happens in one go, you're free to refund credits and upgrade something else mid wave. Not by pressing the refund option but the - (minus) icon in each upgrade.

It's a slow process but a very big life savior.

For example, at the beginning you can spec only on fire and crit resistances since only pyros and crit melee bots come, but once they're dead and the soldiers are next, you can unspec the fire resist and send the money to blast resist. Fire would not become useful again till near the end and by then you'd have enough money to get by.

This one's more general but you can also change weapons mid wave, something very useful for when you need to adapt to a situation quickly (like swapping rescue ranger for widowmaker during the french invasion). Just remember to refund the money of said item and put it into the one you wanna use.

There's also the last one which is less straight forward

If you don't care about stats like damage and just want to help beat the mission, you can change class mid wave by typing "retry" in console. This will automatically disconnect and reconnect you to the server and you'll be able to pick another class. The stats will be lost but the money will remain there

DISCLAIMER: DO THIS ONLY AFTER REFUNDING EVERY UPGRADE YOU HAVE IN YOUR CURRENT CLASS.

This trick is useful for spy in particular. More on that later.

GENERAL TERMINOLOGY:

-Spec/Unspec: buy upgrades or refund them
-DPS: damage per second, basically how much you do in the least amount of time.
-Pop: pop uber, when medbots activate their ubers.

MONEY

One thing to note here is while in other missions money collecting is a necessity, in wave 666 you get 5k at the start, and since the wave has no stops, any class that spends most of the time on the front line such as soldier, demo or pyro and even medic (or if the team has a good sniper) will end up picking sufficient money to get by (save for one class but more on that later)

Another thing to have in mind is that PLEASE pick up money if you see it. Doesn't matter if you have 5 scouts on your team (for some reason), if none of them is around then pick it. Scout isn't omnipresent, he can't be everywhere at the same time. So many times i've seen people completely ignore money that is right in front of them or very close after killing a bot at point blank because "meh the scout will get it".

This task becomes increasingly worse for scout when the team scatters and there's kills happening all around the damn map, which is why it helps the scout more (and the general effort really) if you keep kills packed in one area.

Get the cash, help your fellow scouts.

THE MISSION'S STRUCTURE

One big run to the end through a seemingly never ending horde, here's the order in which they'll come:

1: Giant eyelander crit demoknights in groups of 4 accompanied by crit bat scouts and non-crit pyros.

Once you kill sufficient pyros and scouts, only the giant demos will come until they're all dead. This is a very good dead time to go buy some upgrades if you feel like it. NOTE: avoid getting hit at all cost, just because they're demoknights doesn't mean they can't kill you quickly.

2: Giant crit soldiers, all 10 of 'em accompanied by a stock medic bot.

A sniper, demo or a gas pyro can take out all meds without a problem and they should, dealing with these soldiers wont be a problem once they're all gone but please hold your fire if you can't take out the medics instantly like the 3 mentioned classes can. Once all soldiers are gone, it's a good small dead time to go buy upgrades.

3: Giant non crit soldier and heavy accompanied by non-crit soldiers and heavies.

This is the first difficulty spike of the wave, since both of these classes do good enough damage to shred through any unprepared player (and engie's buildings as well). Once the normal bots are gone, once again it'll be only the giant pair of soldier/heavy. Some classes can take the chance to go get some upgrades.

4: 3 tanks and crit scattergun scouts.

Here we can have a bit of a split of the team. Engie can stay behind to keep the bomb guarded, something he wont have a problem doing since it's only scouts swarming alongside the tanks. Another player (or the engie himself) can pick up the money the scouts drop. Meanwhile, the rest of the team can focus all their power in taking down the tanks or go get some upgrades even.

5: Giant non-crit demoman in groups of 4 accompanied by crit eyelander demoknights and 1 tank

The previous round got an upgrade, now you have to deal with giants specifically designed to deal with engie, so the bomb is gonna need more protection now. Since it's only 1 tank, a single phlog pyro can take care of it just fine while the others deal with the giants, which are more of a threat than the tank.

6: Buff banner direct hit soldiers

Get ready to hear "sentry down!" a lot 'cause these soldiers will make engie's life a nightmare and any other unfortunate class that didn't upgrade blast/crit resistance, and even then, these rockets will hit very hard. There's no giants or tanks here so it's regular horde killing until they're all dead.

7: 4 pairs of 1 giant crit deflector heavy and 1 giant quick fix medic.

This is the part where a lot of people mess up, 'cause projectile classes are suddenly rendered near useless and the medic needs to be taken care of 'cause no matter how much damage you throw at the giant heavy, his health bar wont even bat an eye. The medic must die first and he has to go quick, 'cause if he gets low on health he'll pop uber unless taken out fast enough.

Demoman, sniper and spy shine here, they can easily take out the medic and after that, the giant heavy becomes a free kill like any other giant.

Since they're the only ones to come during this segment and there's no other small robots, some classes may opt for an upgrade.

8: THE FRENCH INVASION.

This one's definitely the part you'll see people fail the most, since 4 tanks come accompanied by 96 SPIES. While a spy may seem like a free kill, a swarm of that many will catch slacking a lot of people. Here your team can do 2 things.

A: Focus on tanks while avoiding the spies.
B: Speedrun french killing and clear all spies out, THEN focus on tanks.

The first option requires classes such as medic, sniper, spy, engie and heavy to get on top of the tank if they want to damage it without being disturbed. Scout, soldier, pyro and demoman are mobile enough and/or have enough splash damage to kill spies while also damaging the tank. Just be sure to shoot at everything that is moving and to look behind.

The second option is risky, but it can work. A pyro with a bit of help from splash damage classes can clear out all 96 spies fast enough to then allow the entire team to focus on all 4 tanks freely. Of course by the time they all die, the tank will be near the hatch so be ready to buy crit canteens.

Also there is a very rare (but still possible) scenario in which a spy can end up picking up the bomb and carry it to the hatch. If this happens, then every other spy will attempt to do so if they can which can result in an unexpected defeat when dealing with the tanks, since the bomb is usually a non-issue during this part of the wave.

NOTE: EVERY ENEMY FROM HERE UNTIL THE END WILL HAVE CRITS. ALL GIANTS HAVE BEEN DESTROYED. ONLY NORMAL ROBOTS FROM NOW ON

Second half of the wave

9: Huntsman snipers. Rain of arrows.

By this point of the wave you'll have most of the upgrades you want which better include resistances, but a thing about these snipers is that, even with full damage resist their arrows will still hit significantly hard, so you better kill them more than they can hit you, 'cause health on kill will come very in clutch for this part.

10: Soldiers. The night of the thousand rockets

Rip your frames for this one if you have an old gig. The rocket spam is tremendous and also very disorientating since even if you survive a hit, you'll be sent flying across the map which can make killing them a bit of a hassle. Dealing with those rockets using the medic's shield or the engineer's short circuit can help a lot. You can also draw aggro from the soldiers so the rest of your team can take 'em out if you're playing as a class perfect to do so (scout/spy)

11: Demoman. Carpet bombing

Take what i said about arrows hitting hard and apply it here except demos have more hp and their pipes can still hurt you even if they miss. On the bright side, they don't clutter the screen as much as rockets and avoiding pills is easier so killing them in general is much better.

Note: pyro's might want to swap phlog for stock if they wanna help with airblast, but only if your team is desperate.

12: Pyros. Into the inferno

Special care pyro players must have when these come, 'cause just because you have built in fire resist, even if you get the fire resist upgrade and crit resist, these pyrobots can still melt you down fast. Luckily pyros suck at range so the engineer can just sit back, laugh and let the sentry and heavy deal with them. Projectile classes better exercise caution tho, 'cause these bots can airblast and will do so with extreme prejudice.

13: Scouts and the last tank

Same as above except even easier. These scouts are mostly filler and easy pickings compared to everything you've had to deal with so far, and a last preparation of what's to come. A tank will enter the map when there's around half of scouts left, this is the last one and the other bots in the arena are little threat so feel free to throw at it everything you got. And you better do it quick 'cause the following part has ended many runs before.

14 and last group: +20 heavy/stock uber medic pairs.

While it was easier during the giant soldier/medic pairs to take the meds out, this time it's only small bots that come in scattered groups. Not only that but people will often make the meds pop uber here very easily. Most importantly, these pairs will drop even with scouts still in the map, when there's around less than 10 scouts left, so they tend to catch people off guard 'cause you go from dealing with tiny man to deal with a pocketed beast firing lasers.

DO NOT underestimate these pairs 'cause they can overwhelm a team very easily. A sniper can stay behind while the others kill the scouts and the tank to deal with as many of 'em as possible. If the situation requires it, airblast can help too. Otherwise, kill until the last one of 'em drops. You got the money, feel free to use it to buy uber canteens or crit canteens if you're confident in one shooting the meds.

CONGRATULATIONS! YOU JUST BEAT WAVE 666! Feel free to taunt and/or jump into your nearest pit.

Team composition and side notes about some classes and their weapons.

NOTE ABOUT WEAPON RECOMMENDATIONS OF EACH CLASS

There's many tier lists for best mvm weapons which cover the entire arsenal of TF2. Weezy's tier lists are pretty good at that so you can feel free to look up his videos on youtube (https://www.youtube.com/c/WeezyTF2). On this guide i'll go only over the meta and some sidegrades rather than describing the usefulness of every item.

NOTES ABOUT TEAM COMPOSITION

It is said that any composition is good so long as all players are good, and it's true! but for public lobbies wave 666, you're most likely to find anything but good players.

What you need to do here is make sure your team is balanced in it's requirements:

-Do we have good dps for tanks?
-Do we have good medic killers?
-Do we have an engie?
-Do we have high dps classes for general mobing and giant killing?

Each class has a role, so long as your team covers most of them you should be fine. If you want to help, play what is needed.

Later i'll cover what each class is good at so you make your own conclusions.

CLASS RELEVANCY AND NECESSITY

Scout isn't as critical

I did say originally how wave 666 gives so much money even normal front line classes can get enough money to get by. This basically makes scout more of an optional pick rather than a must for wave 666.

It's still very welcomed due to his milk and fan o war support capabilities, and also one particular class will be very grateful of having a good scout on the team.

Demoman's hustle

Demoman is a very expensive class to upgrade (the most expensive of them all really), so if you see a demo in your team and go scout, you can be sure they'll be grateful for it.

Medic is useful, but not a must have. This isn't two cities.

Wave 666 gives you plenty of money but also shows you from the start all you'll encounter during your endurance fight. With that much money, you can get all resistances and the health-on-kill upgrade, which becomes an absolute life savior. Hell by near the end, some classes can even afford to buy health regen to become extra spongy.

Medic's shield is useful, his kritzkrieg can turn giant killing into a joke, he is a very solid pick for wave 666 but he isn't the MUST have people seem to think he is, at least not for this mission.

Get upgraded, get killing, be smart in your aim and movement and you'll hardly die.

Spy isn't needed on wave 666
Here's where i have to make a very very depressing note about spy's relevancy in wave 666.

Spy is an excellent giant killer, i'd say he's the best when it comes to handling giants 1v1 (for groups of giants, demo and sniper reign supreme), but the sad reality of spy in wave 666 is that he's only useful for half the wave before becoming completely outclasses by everyone else.

His sapper is outclassed by milk and jarate.
He'll get at best 3 or 4 backstabs before either having to dead ringer or die while other classes can take out much more.
He lacks any decent dps against tanks.

Spy is not a bad class by any means, he has a role and he fits extremely well at that, but he's just too specialized for wave 666. Someone playing spy is better off picking sniper or demo if their intent is killing giants.

If you really want to play him and help, you can use the "console retry" trick to play him during the first half of the wave, and then switch off to another class for the rest of the wave.

Scout

1: ROLE
Scout is best known for being the best money collector in the game, as well as a great support class when it comes to healing and dealing with giants. Picking money overheals you up to 700hp and also you have a money magnet, meaning that you don't have to go over the money directly to pick it up.

Picking money not only helps your team but keeps you alive as well, so this is a good incentive to do your job.

The upside to scout of wave 666 is that, with so much money, he's able to break outside of his usual support role and be more flexible from the get go, rather than waiting for later waves.

2: WEAPON RECOMMENDATIONS

Primary:
-Soda popper: an absolute beast and with mobility enhancements. Ghost upgrade it if you wish as well (Equip stock, go out of spawn, equip soda, go back and get to the store, buy 1 tick of jump height then 1 tick of firing speed, accept and done, your soda popper does extra 10% firing speed)
-Shortstop: dps wise this thing is almost as potent as the soda popper while also having the benefit of not needing to be in someone's face to do full damage. Shove is useless tho.
-Scattergun (stock): the good old reliable. Nothing wrong here although get ready to reload a lot.

Secondary:
-Mad milk: scout lives and dies by this weapon. It is his single biggest contribution to mvm in general. A must at all cost
-Crit-a-Cola: The use this thing has is for wave 666 and very specific but still useful. During the french invasion, if you don't want to buy crit canteens and still do good damage at the tank and they're not near the hatch, get the crit a cola, fully upgrade it and then use it to shred the tank so by the time it gets halfway through, it's low on health. (This is of course IF your primary is fully upgraded). After the french and tanks are dead, go back to milk.

Melee:
-Fan O' War: having a giant suddenly take minicrits for multiple seconds is a blessing and a great tool, plus it doesn't need any upgrading to do so (coughsandmancough)

Note: i know the sandman can mark too, but it's too expensive and cuts you max health in the process for something that 1: is not that hard to do that you need to do it from range and 2: is already provided for free in another weapon.

3: UPGRADE RECOMMENDATIONS

The path of support

You can opt for buying all resistances (fire, blast, bullets and crits), fully upgrade the mad milk (slow-on-hit is optional) and then fully max your movement. (NOTE: only spec 2 points max into movement speed, the 3rd point is useless on scout since by then you'll reach the max speed the source engine allows)

By then you'll have some spare money so invest it into your main weapon in whatever way you please, but these upgrades will make it clear that your primary goal is to help.

The path of support...through aggression

Buy damage, reload speed, max ammo, max clip size and IF you feel particularly angry then buy bullet penetration. Health on kill is kinda useless unless you're (somehow) struggling to get HP by getting money.

After this, max your movement speed and jump height.

4: STRATEGY

The path of support:

Since your milk is fully upgraded, you can use it all you want so long as you actually throw it to groups of robots. Even with full cooldown upgrade it's a waste to use it on one regular bot.

Giants are a priority, and since the fan o war can only mark 1 target, focus on whoever is carrying the bomb or whichever is on front of the pack.

The path of the angry Boston man:

Scout can be a terrifying dps class when his main weapon is fully upgraded, so your main priority here is to help (and even solo) the giants and any regular bot carrying the bomb. Scouts who play in this style should prioritize their milk for giants, but their way of helping is mainly through eliminating the bots as quickly as possible.

Their enhanced movement will also help them get the money and keep them alive, which becomes much more of a necessity for this play-style since you lack any resistances.

Another thing you can do as a scout is to, when overhealed to the max, bodyblock a giant for a brief period of time before the overheal gets shot away.

Oh and get the money, that one should be obvious. I know what i said about money early on the guide but hey, since you're playing scout, might as well get the cash. It's always helpful to give your team mates that one extra 50 bucks.

Soldier

1: ROLE

Soldier is a jack of all trades type of class. He can do good damage at all ranges (provided you spec into rocket specialist), deal with tanks if upgraded enough and also destroy giants with relative ease.

He's very adaptable and flexible to whatever you need him to do, although with a bit of a money need since his main weapon requires good investment to do good.

Go where the bomb is or where you're needed if the need is to kill robots.

2: WEAPON RECOMMENDATIONS

Primary:
-Beggars bazooka: soldier's most powerful weapon and top 3 most powerful ones in mvm overall.
-Air Strike: a burst damage demon that requires heavy money investment.
-Stock: the good old reliable, same as the scattergun although requires good amounts of money as well.

Secondary:
-Buff banner: the best defense is offense
-Concheror this can be very helpful if the scout isn't around to provide milk support or if you need to quickly get to another position to help.
-Battalion's backup if you really need help 'cause people are dying a lot, or you have team mates who haven't bought resistances for any reason, this can be very helpful and also becomes a life savior during the second half, since this banner denies crits.
-B.A.S.E jumper: air strike exclusive, only ever use it with it.

Melee:
-Disciplinary action: good for helping your team mates get to the front quicker if you don't have the conch.
-Escape plan: good to save yourself, heal and get back to the fight quick.

3: UPGRADE RECOMMENDATIONS

The all rounder patriot:

Beggars is a special case since not only is the most powerful weapon soldier has, but it's also very cheap to upgrade to it's fullest potential. Max damage, reload speed, ammo and buy 1 tick of rocket specialist if you feel like it, but with the previous 3 is already pretty good to start with.

Note: when using the beggars, don't wait for all 3 rockets to load to fire them. Just tap the click repeatedly as if you were firing a semi-auto weapon. The load is not bad (it can be quite good when the clip is fully maxed against giants) but the click tap trick is part of what makes this weapon so powerful.

Then max your banner, after this, spec into whatever resistances you wish.

The hell giver eagle:

If you feel like tanks and giants are the most horrendous thing since the nerf the bison got and just NEED to unload all your anger onto them, the air strike is your go-to. it needs A LOT of money investment (damage, clip size, firing speed, 1 tick of rocket specialist, max ammo, reload. All maxed) but when it needs to perform BOY does it perform. There is no better feeling as a soldier than unloading 16 crit rockets with full damage and firing speed on a tank.

Whatever money you have left to spare (wont be much really since majority of it will go to the air strike) buy resistances. You're gonna be particularly frail for a while with this playstyle.

Of course you better compensate with proper damage since you wont be helping your team with a banner.

4: STRATEGY

The all rounder patriot:

Pretty straight forward. Kill robots, deploy banner EVERY TIME you can, be near your team mates and help with the tank.

The hell giver eagle:

Giants and tanks are your priority, yes, but this does not mean you can't do well against small robots. A single barrage can clear out a group of them with ease. Just be sure to be near where the dispenser is 'cause you're gonna need it a lot. Also crit canteens are a must, this is a very highly demanding style money-wise but can also deliver substantial dps to deal with the horde.

The banner triage:

If there are other 2 soldiers in your team, coordinate so each of you uses one of the different 3 banners (Note: banners don't stack, with 1 each is enough.). Deploying all 3 banners gives an incredible boost to the team overall and it's a great offensive/defensive/support force to be reckon with, plus a very fun play-style as well! Nothing like the sound of the 3 horns ringing to lift the spirit.

Pyro

Boy am i gonna have to make multiple disclaimers, notes and warnings on this class since pyro is so much of a noob trap (and i say this being a pyro main).

1: ROLE

Pyro is an excellent crowd controller, average giant killer and the best tank buster in the game, also a very cheap class to upgrade and get to a good level to be effective.

Kill all robots, guard the bombs, but as soon as a tank enters the area you have to go get it. You're the best one at it so get to it.

He's also a very good medic killer (small ones that is) but this point is controversial due to reasons i'll get to later.

2: WEAPON RECOMMENDATIONS

Primary:
-Phlogistinator: the single best tank buster in the game due to having crits on demand.
-Backburner: keeping the ability to do crits by taking advantage of bot drops while also being able to use airblast in very few occasions. It's the best middle ground between stock and phlog.
-Stock: this one's in case you want to use airblast much more, but you MUST be very VERY careful on when to, more on that later.

Secondary:
-Gas passer: overpowered item that can completely delete the small medics and any other small robot at the cost of essentially nothing. Don't get cocky just because you can do that tho.
-Detonator: excellent for mobility while also keeping enemies on fire at range. Flare jump away if you need to get to another position quickly or gain upper ground.
-Flare gun: very good burst damage to deal with giants if you don't wish to go in with your flamethrower and risk dying.

Melee:
-Powerjack: if you need extra mobility this is a good choice.
-Homewrecker: if you feel like a pybro and wanna help your fellow engie, this is the go-to

3: UPGRADE RECOMMENDATIONS

Crowd controller. Tanks destroyer:

Upgrading pyro to do both doesn't require a specific extra course in your upgrade path, so you're safe to go for the same. Max damage, max ammo capacity, health on kill. Then, go with movement speed and resistances.

The secondary upgrade conundrum:

IF you're using gas: explode on ignote. IF you're using detonator then reload speed. IF you're using flare gun, then reload speed, firing speed and max ammo for later.

4: STRATEGY

There's not really much to do as pyro other than tanks. Kill robots, help your engineer from time to time if you have the homewrecker and when the tank comes, melt it.

There's a very particular way of maximizing the damage you do to tanks, as seen in the picture bellow:

What you need to do is stand in front of it, crouch and aim up to near the edge of the tank. This way you'll deal the max damage to it.

When it comes to dealing with giants, pyro players may end up just rushing in to end up dead 1.2 seconds later. You do not need to be in your enemy's faces to kill them quicker, know the range of your flamethrower and take advantage of it..

What to do against a giant instead is to run in circles around it. Maximizing speed movement helps a lot here. Or if you feel like it's not worth going in, you can use the flare gun as a very effective range tool to deal with giants.

IF you have the regular flamethrower or the backburner, you can use airblast IN VERY SPECIFIC SITUATIONS to help your team, such as pushing the sentrybuster away TO AN AREA WHERE THERE'S NO TEAM MATES, or pushing the bot carrying the bomb into the pit to reset it. And there's also lastly pushing the bomb carrier away from the hatch in case the situation gets too bad.

The phlog has a very particular trick to using it, which involves activating the mmfm and skipping the taunt animation to get both uber and crits.

To do it, you need to jump into a giant or the back of the tank, activate the taunt and, if you do it right, you'll immediately fall down from the giant/tank, skipping the animation and keeping both uber and crit and also gaining some precious seconds of crits (since the meter starts draining when the taunt begins, not when it ends)

5: WARNINGS ABOUT PLAYING THE CLASS. THE DOs AND DON'Ts

Ok i'm gonna have to do multiple clarifications here about the class.

Pyro is a great class and has his place in MvM, yes, but there's a reason it has garnered a reputation for being a noob trap like engineer has (more on that on his class page).

Just because you can shoot fire doesn't mean you're an immortal god. So stop charging into the enemies, pyro can be quite squishy and very frail when facing hitscan classes (Giant heavies can AND WILL shred you if you're not careful), besides that, his flamethrower is not as powerful as it seems, specially after jungle inferno. KNOW YOUR LIMITS AS A PYRO

The gas passer

First of, i need to clarify that i do use gas on a regular basis, i have no problem with anyone using it, and i DO agree that it's overpowered and needs a nerf to it's prices (splitting the explode damage into 3 250 credit upgrade points maybe). Having said that, i provided upgrade tips for both detonator and flare gun 'cause, in case you do not want to use gas, both flare guns are still excellent choices for pyro.

Detonator provides a great mobility tool while also being able to set multiple enemies on fire at range, rewarding detonation time.
Flare gun is a very good range burst damage tool for pyro in case you don't feel like rushing into the giants.

If you don't like the gas passer for moral reasons, then detonator and flare gun are your go to.

Knockback mechanics.

This is also another one of pyro's tools that will make half the server want to strangle you if used too freely (in particular the sniper will hate you and you'll be banned from australia).

Knockback on pyro can be an excellent mechanic and a life savior WHEN USED RIGHT, but what you need to understand is that it can also mess up big time your team mates. Here's some examples.

-Sniper can't hit anything now.
-You moved the giant away from the sticky trap and the demo wasted 14 crit stickies.
-The heavy is far away from the giant and doing insignificant damage to them.
-The engie ran away from the sentry buster succesfully with his sentry, but you just airblasted it near him again, or your team mates, or other buildings of the engie.

Also as you can guess, this applies to the scorch shot as well.

Be very VERY careful of when to use knockback. Know your team, the timing and you should have no problems with it and everyone else, 'cause on wave 666 given the spam you'll recieve, airblast can have it's moments in case you don't want to use the phlog.

Demo

1: ROLE

Blow stuff up. That's your job.

Demo has the potential to be one of the most destructive classes in MvM if played right. Giants become non-existent and tanks struggle to even gain a few meters of territory before blowing up.

This comes of course with a big issue: money. Since demo has essentially 2 primaries, both require heavy investment to perform to their fullest, and while wave 666 has lots of money, it still doesn't have enough to get both launchers to max performance capacity. Maybe by the time the pyros come near the end but that's already too far late into the wave.

Sure there can be money management strategies (if a scout is helping in your team that is) that can allow you to get the most out of both, but for the sake of simplicity, i'll cover an easier way of starting up with the class and perform to the fullest in 666.

2: WEAPON RECOMMENDATIONS

Primaries:
-Grenade launcher (stock): Reliable and everyone has it. Can't go wrong with it really. The advantage of the rollers comes very in handy during the 2nd half, when you can just stay on the roof of the building facing the straight in which robots come from and just shoot pipes like there's no tomorrow.
-Iron bomber: If you don't mind sacrificing rollers and explosion radius 'cause you want to get the most damage by landing direct hits, then this is the go-to.
-Loose cannon: i have to place a disclaimer here. This primary is useful FOR ONLY ONE SET (the sticky launcher one, more on it later). The strat with this weapon is to lay down the sticky trap, then with the cannon shoot at the giants before they drop into the map (while they're still invulnerable). The loose cannon's knockback will send them back and group them together more, ensuring more (if not all of 'em) get blown up by the trap. It's a very useful tool to group together giants but it is NOT an offensive weapon, do not rely on it for heavy damage, that's what the sticky is for.

Secondaries:
-Scottish resistance: another absolute unit of mvm, a total monster. 14 crit stickies at max damage will vanish anything except for tanks, and even tanks will cry at suddenly having 1/5 of their health gone in one instant.
-Sticky launcher (stock): if you're more of a spam enthusiast or just cannot stand the slower arm time of the SR then stock will do just fine.

Melee:
-B o t t l e: it's...it's a bottle, good ol' scrumpy. Might get a kill or two on a pesky spy or sniper. Drink irresponsibly for better performance.
-Eyelander: There's a risky strat with this one. You may want to invest some points into it to make it perform better at first, go and get 4 heads then come back and refund those sword points and send them into your standard weapon. Now you're a faster demoman with 210 HP. It's really useful but be careful with it.

HYBRID DEMOKNIGHT:

Primary:
-Grenade launcher (stock): Same as above.
-Iron bomber: Same indeed.

Secondary:
-Splendid screen: if you wish to spam this more then use it.
-Charge n' targe: very useful for the extra resistances if you can't afford 'em.
-Tide Turner: the lack of crits on charge is meaningless when you can just get a crit per kill. Use it if you want to have extra mobility.

Melee:
-Zatoichi (katana): my personal choice when running this set. Saving health on kill money is very useful and i can just enhance my own movement speed. By late wave, getting health on kill on this thing becomes overkill and you turn into a sponge of damage (if you can manage to keep landing kills that is.)
-Eyelander: almost as fast as a scout and 210HP, getting the 4 heads becomes much easier here and the extra HP and speed can help you be more agressive.

3: UPGRADE RECOMMENDATIONS

Carpet bomber:

This set focuses heavily on the grenade launcher, so invest into damage, reload speed and firing speed for a good start, a bit of ammo too if possible, then fire and crit resist. Afterwards, aim for clip size asap and the rest of resistances.

Demolition man:

This one focuses on the sticky launcher instead. Max damage then reload speed. Using the scottish resistance has the advantage that it already comes with better ammo reserve and firing speed, so you can instead opt to upgrade something else. NOTE: only 2 points of clip size are needed for the scottish resistance, because at that point, you can fully deploy a full 14 sticky trap without needing to reload.

If you wish to use the sticky launcher instead, max damage, ammo and reload speed are a good start, then go for fire and crit resist. Whatever's left, send it to health on kill and/or firing speed.

The torgue knight:

This one's gonna focus on your knight part of the hybrid set. Damage, crit on kill and firing speed are A MUST to make this set kick off with a good start. The zatoichi will save you health on kill money. Then invest into fire/crit resist and then buy movement speed. Your set of course for the rest of the wave is upgrading the resistances then your primary like you would do with the carpet bomber set.

4: STRATEGY

Carpet bomber:

You have a strong weapon to start with but need to be careful until you can get more resists and health on kill, but the benefit of the pipes is that even when missing they can still hit. Giants are still gonna take a heavy hit from you. Grenade launcher will help ya if you want more explosion radius and loose rollers. Iron bomber if you want improvised sticky traps and to hit direct hits more reliably.

Demolition man:

In this one you can get a kill or two with your stickies on normal robots, but that's not gonna be your main focus. Your main focus is to make sure giants enter the arena half dead or completely gone. Set up the traps and wait for the right moment then detonate. A kritzkrieg medic is your best friend since it can save you precious money from crit canteens which are pricey. If you see a kritz medic tell 'em to uber you before the wave begins then laid down the trap. Hardly anything survives a full crit trap.

NOTE: crit canteens in general are a must for demo regardless of set, and while a kritz medic is very useful, you can't expect to have one up your ass 24/7. Buy them but use them sparingly. If you're going bomber then save 'em for giants (SPECIALLY THE GIANT MEDIC). If you're demolition then use them only to laid down crit traps and use them exclusively for the giants and tank.

The torgue knight:

I know this may seem odd at first, like one would not expect to see demoknight to be viable in mvm, but i'd argue he is with the right armount of money, and luckily for us, wave 666 provides just that. A fully swing speed+damage upgraded sword with crits can do a very surprising amount of damage to tanks, and if tanks get to feel the hit then small robots are no issue. Sure you may struggle against giants which are part of your job as a demo, but that's exactly what the grenade launcher is for.

In fact, the crits on kill upgrade is arguably what makes this entire set work. Get one kill then start a chain reaction on robot after robot, or you can switch to your grenade launcher and use it on something else, or get a kill then start swinging wildly into the tank (try it during the 3 tank+scout part).

NOTE: past the french invasion, uber canteens are gonna become a must.

I would not recommend this 3rd set until you have more practice with the class, but do not mark it off as non-viable 'cause it definitely is and very fun as well!

Heavy

1: ROLE

Be the giant's nightmare. Sure demo can blow 'em up in an instant, but heavy gets to look at 'em in the eyes before killing 'em, and they will know there's nothing they can do about it.

Heavy is a beast when handling normal robots and SPECIALLY giants, while other classes require tons of upgrading to make their weapons do better, heavy's minigun requires minimum investment because it is already a beast.

Instead, invest into becoming as durable as possible. Resistances, health on kill, even health regen if you feel like flexing your money 'cause heavy is also a very cheap class to upgrade and get the fullest from. All in favor of not only shredding through robots, but also make sure THEY DO NOT CROSS YOUR LINE.

2: WEAPON RECOMMENDATIONS

Primary:
-Brass beast: this is it, this is peak mvm damage. If i had to make a top 3 for the most destructive mvm weapons, brass beast would proudly take the podium with the beggars and the scottish resistance. It's the only minigun that has a built-in damage increase at the cost of a movement penalty you wont even care about since your main job is to be a human barricade.
-Stock: In case the movement penalty is still too much for you to deal with, stock minigun will perform just fine and allow you to be more mobile

Secondary:
Buffalo steak sandvich: excellent pick when you wish to help your team deal with the tank while using the warrior's spirit.
-Sandvich: sandvich makes you strong. Sandvich heals you and your team mates. Sandvich good. You're not gonna be using it much really but it's still the second best heavy has in his secondary repertory for mvm.

Melee:
-Warrior's spirit: since heavy is mediocre against tanks, this is his best tool to deal with them. Equip if you really wish to help with tanks.
-Fists of Steel: If you trust your team mates enough to deal with tanks, then the FoS will save you during retreats due to it's immense damage resistance.

3: UPGRADE RECOMMENDATIONS:

The unmovable bear:

Fully max your resistances, invest into max ammo, health on kill and 1 point of firing speed for your minigun, then send the last for movement speed. During the wave, buy max swing speed if you have the warrior's spirit, otherwise buy destroy projectiles and bullet penetration.

NOTE: do NOT invest into more than 1 point of firing speed since this upgrade is bugged. It actually has no effect past that and it's not worth the investment.

4: STRATEGY

The unmovable bear:

Your main job here is not only dishing out massive damage to the horde and giants, but also make sure to make their lives are as miserable as possible when it comes to moving the bomb. By this i mean that you need to stand directly in their path and block them with your body (body-block), keep an eye on the bomb and kill anyone coming towards you carrying it, forget about any other robot unless they're directly attacking you.

Bots will naturally gravitate towards the bomb, so as soon as the first carrier dies other will come to pick it, keeping you alive thanks to health on kill. The closer they get to you the quicker they'll die. The closer anything is to heavy the more damage he'll do. Heavy MUST be on the robots face to maximize his damage.

When giants come, block them as well but you may need the help of your team mates to pull off a successful block. A scout, spy or engie's sentry drawing aggro from it, a scout milking it or a soldier deploying conch. Anything that keeps you alive and close to the robot stopping it's movement will help you. If none of 'em are present, your sandwich and the robot's attack will help you.

If you get too low on HP and are about to die, stop shooting then jump and crouch and let the giant's attacks push you back to retreat quicker. Eat your sandvich then play cat and mouse until it dies.

Uber canteens, crit canteens and medics are your best friends in these scenarios. Ubers for when you're alone. Crit if the medic can already uber you or you're confident enough that you can kill it with minimal help. Medic's shield will buy you precious time as well.

NOTE ABOUT TANKS: unfortunately heavy is too powerful and valve knew this, which is why tanks have a 75% damage resistance against your minigun, making heavy a not optimal class to deal with them. Your best option if you wish to help is to get the warrior's spirit and max swing speed. This is heavy's best strat to deal with tanks (with crit canteens into the equation, you can do some very respectable damage).

The absolute biggest powermove you can have is standing in front of a giant blocking it, while the giant is under the effect's of scout's milk. You'll heal instantly any attack it does to you while it's unable to move past you. You have become a destructive force of nature. You're immortal. You're the heavy weapons guy.

Engineer (Role, weapon and upgrade recommendations)

1: ROLE

Engineer is probably the single most important class in MvM. He offers a support no other class can provide thanks to his dispenser since ammo consumption can be a very big issue for a lot of classes and play-styles.

-Air strike/beggars soldier
-Heavy
-Pyro
-Sniper
-Demoman

And many more that chug up ammo like there's no tomorrow will find in engineer an absolute life savior.

Your sentry sure helps and the teleporters too, but the dispenser is engie's most important characteristic. So long as it's up and running, so will your team mates and they'll be able to do much more than the sentry.

Other than that, the sentry is also an excellent horde killer due to having aimbot, which makes engineer the best class to guard the bomb while the rest of your team mates fight somewhere else (such as during the 3 tanks+scouts part). Another thing you can do is to block giants with your sentry in case there isn't a heavy around.

2: WEAPON RECOMMENDATIONS

Primary:
-Rescue ranger: excellent utility tool for multiple reasons, it really does it all. Yoink the sentry from the buster, heal buildings at range, combo wrangler jumping and sentry moving, play aggressively, fill your taxes, commit treason, re-build yugoslavia.
-Widowmaker: an excellent tool during the french invasion and i'd say it is also very good if you don't feel like using the ranger (for some reason) since not only it is very cheap to upgrade, but it is also engie's best offensive weapon for self defense.

Secondary:
-Wrangler: triple your sentry's HP, double the dps and allow it to hit what you want. Also ideal if you want to block with your sentry.
-Short circuit: In case the 2nd half of the wave is giving you a bad time. Be ready to get metal tho 'cause this thing chugs it up fast.

Melee:
-Wrench (stock): since you can maximize the hit speed while keeping the building heal rate, stock wrench is the ideal choice for engie in mvm in general.
-Jag: if you don't feel like buying building rebuild canteens and are confident in re-building your stuff fast enough to keep helping then use the jag, even tho you may want to be extra careful since it wont be as effective to block or heal as stock.

3: UPGRADE RECOMMENDATIONS

The walker texas ranger:

Max wrench hit speed, then go to your buildings tab and max metal capacity, building health, buy 2 way tele and most importantly: MAXIMIZE DISPENSER RANGE FOR THE LOVE OF GOD. After this, buy crit resist and 2 ticks of both blast and bullet resist. This is off to a good start and pyros should not even reach you anyways.

Later on, besides maxing your resistances, you should consider maximizing the reload speed, firing speed and max ammo of the rescue ranger. It can really help you for emergency heals when you're in a pinch.

NOTE: Same as heavy, buying more than 1 point into firing speed for your sentry does not actually work, so don't.

Engineer (Strats and common mistakes)

4: STRATEGY

BUILDING PLACEMENT.

TELEPORTER ENTRANCE:

Be sure to place it in the middle of both spawn doors so regardless of where you re-spawn, you'll reach the teleporter in the same amount of time.

TELEPORTER EXIT:

This one can have multiple positions.

If you have a sniper in your team, you need to help them reach their optimal position as soon as possible, so be sure to place it here:

If there's no sniper, i'd recommend 2 positions that depend on what path the bomb carrier is taking (follow the blue arrows before the match begins to know)
In this case, the bomb carrier is following this path, so be sure to place it near it in a safe spot such as this one
This other one is in case it goes the other way.

DISPENSER:

The most important one. It needs to be both safe enough and close enough to the front-line to help your team mates. For that i'd recommend two positions which depend on how your team is doing:

Standard position according to where the bots are going:

Position IN CASE your team mates are doing really well and playing agressively:

Having covered the best position for the buildings, now we move on why you're supposed to be in the way of the bots carrying the bomb.

Engie can be a good blocker too, plus, it is always the best strat to make the bots movement as hard as possible, you must make it difficult for them to follow their path.

This wave has A LOT of spam, so your wrangler can help you tank these hits and also help you fight giants (it is engie's best tool to deal with giants anyways, since a fully hp maxed wrangled sentry has +2k HP. Still, do not get cocky and know when to call it back with the ranger).

In case you wish to help during the 2nd half against the spam, the short circuit can help, but during the first part the wrangler is a must.

You also need to stay behind guarding the bomb when there's a split of bots/giants and tank coming.

IN CASE THE SPAM IS TOO MUCH AND YOU'RE STRUGGLING TO KEEP YOUR SENTRY ALIVE:

Something you can do is that, instead of letting the sentry have a sight line to the entire straight, you can put it a bit back around the corner in the area your dispenser is. This way, bots will have much less reaction time and distance to hit you and the sentry, making it easier to kill 'em.

You can also just take it back, repair it and place it again. Don't worry about the deploy.

THE FRENCH INVASION STRAT:

This is without a doubt a nightmare for engie. 96 spies pretty much ensure your buildings will always remain inoperative and there's still 4 tanks that need help to be taken care of.

Widowmaker is your life savior here. Refund everything from the ranger and fully max the widow, buy crit canteens, jump on top of the tank and start shooting. It is the best engie can do during that part until all spies are gone. This basically means that yes, you're gonna have to forget about your buildings. The tanks are a priority above all and every bullet counts.

SENTRY BUSTERS: if a buster is coming, do not bother trying to kill it unless your team mates somehow manage to absolutely demolish it, but do not rely on this since it's rare. All you have to do is wait for it to come to your sentry, and once it begins detonation sequence, pick it up and RUN. You should have enough time to get away safely and go back to place the sentry and keep fighting.

This is why you make sure your sentry and dispenser are separated enough or have any surface between them, since you wont be able to save both unless you're really good with the rescue ranger

If you have the rescue ranger, you can just take it from a distance when detonation sequence begins and proceed to laugh.

5: WARNINGS ABOUT PLAYING THE CLASS. THE DON'Ts

Like pyro, new engineer players can make lots of mistakes that will end up costing the match to the entire team, so i'll cover here what you should NOT do under ANY circumstances.

For starters... THIS:

There's so much wrong in this picture i even felt awful replicating it so i'll proceed to unpack all the errors here:

-Most upgrades went to the pomson
-Dispenser has no range
-All my buildings are packed together
-I'm turtling in my own spot rather than helping my team mates
-I'm being selfish with my dispenser and having it for myself
-I'm in one of the roofs instead of blocking their path.
-I forgot this when i took the picture but imagine if i built that nest ON LAST (the hatch)
-Disposable sentry
-Disposable sentry
-DISPOSABLE SENTRY
-D I S P O S A B L E S E N T R Y

1: Upgrading your primary does not help, you're not a power class. The only times it is worth upgrading the primary is the widowmaker during the french invasion and the rescue ranger as the wave goes on but not instantly, and it is ONLY to help heal your sentry. The actual engie isn't a good offensive class so don't upgrade your shotgun/pomson or whatever expecting to do good with it.

2: Dispenser range is what allows your team mates to be flexible in their movement while attacking, SPECIALLY HEAVY. Not hugging the dispenser also ensures it wont get attacked as much or suffer from collateral damage.

3: Packing all my stuff together just makes sure the sentry buster eats good.

4: Never turtle, ever, not only because of the above but because this isn't casual. Bots can AND WILL bust your entire nest.

5: Selfishness with the dispenser is something you should avoid AT ALL COST. Your team mates need the dispenser more than you do believe it or not.

6: Having the high ground is not an advantage here, if robots can THEY WILL ignore you and carry on with the bomb. This is why you stand in their path, not anywhere else.

7: Never build on last, your team needs you, there's no intel here and this isn't 2fort.

8:....

DISPOSABLE SENTRY IS ENGINEER'S WORST UPGRADE. HAVING MORE GUN DOES NOT ACTUALLY HELP IF THE EXTRA GUN IS A MINI UN-REPAIRABLE SLOWER BUILDING (compared to the actual gunslinger mini) SENTRY THAT GETS DESTROYED BY A BREEZE AND CANNOT EVEN BE AMMO REFILLED. IT'S A 500 CREDIT WASTE THAT IS NOT WORTH AT ALL. EVER.

In a more calm manner, this upgrade is not worth at all, you're better off spending the 500 credits into something actually useful, and if you deploy that little thing don't be surprised if your team mates don't trust you. There is no bigger dead giveaway that you're inexperienced in mvm than buying it.

It is ok to make the mistake of buying it, i sure did, many did, so long as you're willing to learn and improve you're good to go.

Medic

1: ROLE

Despite the fact that wave 666 has many ways in which your team mates can avoid or heal damage (resistances and health on kill upgrades), medic can still help in other areas such as giant and tank destruction, while also being very good during the 2nd half thanks to his shield.

So long as you heal everyone and revive everyone WITHIN YOUR POSSIBILITIES (sometimes it is not worth risking your life to go revive the pyro who charged into the front and died 2.5 seconds later) you'll perform the bare minimum which is already good.

As for wave 666...you're gonna need to play more aggressively.

2: WEAPON RECOMMENDATIONS

Primaries in general are something you'll use EVEN LESS in mvm overall, since your medigun can be upgraded to do so many things and you're constantly gonna have to pull it out do either pop uber, deploy shield, revive someone, etc, so the minimum use you give them has to be significant.

Primary:
-Overdose: the mad milk syringes are what sell this thing really. Pull it out quickly, spray a giant a bit with some milk then go back to medigun. It can be a huge help in case scout isn't around or if there isn't even one on the team. Another thing to note is that thanks to the upgrades, you're gonna have full uber more often, which helps a lot in the case of the overdose 'cause with full movement speed upgrade you'll end up with a total of 50% extra movement speed which is huge to either save your life or reach someone quickly.
-Crusader's crossbow: if you REALLY need to heal someone in an instant then the crossbow can help a lot. It'll heal even a heavy in a couple of shots. These situations are for moments when you need to heal multiple people very quickly and don't have a shield, or if they need to go back to the front fast. Another advantage of the crossbow is healing at range, just in case you wanna try nailing that shot into a jumping soldier about to die.

Secondary:
-Kritzkrieg: this is what i mean by playing aggressively. Popping crits as many times as possible (when it's worth using that is) can help the general effort in beating the wave faster. Best defense is offense. Coordinate with your demo to lay down crit sticky traps.
-Stock medigun: 8 seconds of god mode is still a very strong ability, so even if you don't have the kritzkrieg, stock medigun can help you do your job just fine. Plus it'll turn anyone (even yourself) into a bodyblocker.
-Quick-Fix: straight up a shield farm and the most efficient one at it too. You could swap whatever you had on the first half for the second and have an easier time dealing with the spam.

Melee:
-Ubersaw: +25% of uber on hit. Do i need to say more?

3: UPGRADE RECOMMENDATIONS

Medical blitzkrieg:

You're gonna need to max out your resistances, you should be as durable as possible so you can make your team mates last as long. Then max healing mastery, uber rate and duration. During the first part of the wave the shield isn't of much help since only demoknights, pyros and scouts come up which is nothing you or your team mates can't handle.

Shield becomes your #1 priority once the giant demoknight part is done tho, then as the wave goes on, get canteen specialist and mad milk syringes in case you have the overdose, if not, max ubersaw hit speed. This one's very important to have on the list, since you can get back to full uber in a very short period of time.

I'd also recommend movement speed and jump height for later.

4: STRATEGY

The canteen provider:

Canteen specialist is a very powerful perk that allows you to buy canteens for a cheaper price and use them to share the effect with your team mates. Heal someone, use your canteen and both of you will get the effect even if you stop healing that person.

If you're using the kritzkrieg, buy uber canteens. If you're using stock medigun, buy crit canteens.

This ensures that you're able to keep someone alive even in the worst of situations for a while. For example, deploy shield 'cause the giant crit heavy deflector is coming and the medic has been taken care of, cool, but the big guy is still strong and you need to help your heavy. When the shield is about to run out, use the uber canteen to give him uber, then go heal someone else who needs it or pop uber yourself on the heavy.

It's all about timing the moments in which you keep people alive.

The shield expert:

Knowing the limits and inner workings of your shield is key. During the 2nd half spam, you need to look down a bit while the shield is active to ensure it is connected to the ground, 'cause the thing about the shield is that, in certain small elevated positions, a rocket can still hit you through splash damage in those very small gaps and kill you or send you flying.

Another thing to note is that fire can go through your shields, so deploying it against pyros is useless.

Something else you can do with it is deploy the shield during high spam moments and use it to protect the sentry. It's like protecting a heavy with aimbot and you can be sure your engie will be thankful for it.

Lastly, if the giant medic/heavy pair near mid wave is becoming a problem, deploy the shield then make sure it's between the pair. The shield will cut the giant medic's beam and prevent his patient from being healed. This will give your team mates the perfect opportunity to kill the big heavy and after that, the giant medic is easy pick.

The uber leech:

Once you have full ubersaw hit speed, you can attempt getting a bit more aggressive with your uber farming. Sentry busters are your best friend here since they're basically a mindless non attacking uber battery. Run up to them and hit them until your uber meter is full, then let it blow up. (Needless to say but be careful when doing this, you want to run away safely in time before detonation.)

You can also attempt at getting the ubersaw hits on giants that are not attacking you, or small robots like snipers or scouts.

NOTE: you wont get uber from disguised spies.

5: UBER, HEALING AND REVIVE PRIORITY LIST

While i did say that you should aim to heal and revive everyone within your possibilities, some classes are more important than others in certain situations.

For order of priority of what classes you should heal from most important to least:
-Heavy
-Soldier
-Demo
-Pyro
-Engineer
-Medic
-Sniper
-Spy
-Scout

Scout already heals himself by picking money
Spy can fake death, cloak or disguise away
Sniper is often far and safe enough

Order of what classes you should revive from most to least important:

-Heavy
-Soldier
-Engineer
-Medic
-Demo
-Pyro
-Sniper
-Spy
-Scout

Sniper is often too far to be revived
Spy is often too behind the front-lines to be revived
Scout has no re-spawn time so he comes back to life instantly

Order of classes you should use your uber on (Kritzkrieg):

-Soldier
-Demo
-Heavy (ONLY AGAINST GIANTS)
-Pyro (MAKE SURE HE DOESN'T HAVE PHLOG CRITS DEPLOYED)
-Scout
The rest are not worth it.

Uber priority (stock)

-Heavy
-Pyro
-Soldier
-Demo
On the rest use it only to save them.

It isn't to say that never heal the lower classes, this is more about something of the likes of "spy is injured but he can heal with a dispenser just fine, i need to keep this heavy alive 'cause there's a giant here"

Sniper

1: ROLE

Sniper is without a doubt the most powerful class in wave 666 and there's no doubt about it. I've seen snipers reach above 230k damage total when mission is finished. It's simply abysmal the amount of help one good sniper can give.

I've mentioned before how he can be one of the best giant killers, but he can also be an excellent crowd controller in the right hands since giants are always packed with normal robots.

Your priority as a sniper is always going to be the giants, you're the best class alongside demo to deal with multiple groups of them.

2: WEAPON RECOMMENDATIONS

NOTE: Bazaar's bargain, machina and stock are all 3 good choices for sniper, but the hitman's ability of basically turning into an automatic rifle when scoped is not only part of what makes it powerful, but it's also more suitable for new players to start the class with. There are other missions where the other rifles can come in handy, but for this one, hitman's is the indisputable king.

Primary:
-Hitman's Heatmaker: as a sniper, you're gonna need to kill multiple smaller robots thanks to explosive headshot, which means lots of spam and uncharged shots. The rifle's "shoot while scoped" ability let's you concentrate better and you don't have to re-adjust for a shot with each bullet. It may not seem like much, but go ahead and test it when the soldier/medic pairs come and watch as every medic dies and every soldier reaches half of the straight nearly dead at the cost of next to no effort.

Secondary:
-Cleaner's carbine: pick this if you want to help destroy the tank. Shoot at it, fill the "crikey" meter then activate it and swap to the bushwacka to smack the tank to death. Rinse and repeat.
-Jarate: in case you can trust your team mates to deal with the tank, use jarate to support the effort better by having the robots go slower and/or suffer minicrit damage from all sources.

Melee:
-Bushwacka: turns mini crits into crits, and since the two previous secondaries give you or your team mates minicrits one way or the other, you can see where this is going.

3: UPGRADE RECOMMENDATIONS

Bullseye artillery:

Since sniper is most of the time in the back lines, you can go ahead and upgrade majority of the rifle to the max (damage, explosive head shot, reload speed and max ammo) without worrying for resistances. After that, max crit resistance and save the rest.

As wave progresses, if you're gonna help with the tanks, max out the bushwacka's hit speed. If you're going with jarate, max the cooldown. Although by this point soldiers and heavies will come, and while soldier's rockets are avoidable the bullets are not, so you may opt to upgrade bullet resist instead if you're not confident about killing every giant before they get close enough to harm you.

4: STRATEGY

Bullseye artillery:

There's a sniping position which is the go-to for sniper, it'll keep you mostly safe from spies and it'll give you a sight line of the whole straight bots come from. See here for reference:

You need to stand on top of that wooden surface, where the red line is. Spies wont be able to backstab you but when the spy alert comes in, be careful 'cause they're most likely to spawn and go directly to where you are. When you turn around, they'll be running in zig zag bellow you but they can still jump and attempt to hit you (succeeding sometimes and knocking you off the platform) so you better deal with them.

Other than that, the entire bot start zone is your area and your job is to clean the medics as a first priority and then the giants. That's where the beauty of explosive headshot comes in. Any headshot you get, will do damage to any robots nearby (and even insta kill them if they have lower than 190 HP).

"But i'm not good at aiming :(" see that's not that big of a problem here. Bots are predictable, and the biggest threats are also the slowest, not only that but any bot regardless of class carrying the bomb will have it's movement speed cut in half, so even scouts can become easier to hit. Just aim for the heavies really, they're headshot magnets and the rest of the robot's doom.

The way the hitman's heatmaker works is that you don't really need to fill the focus meter to activate it, it can be used at any point so long as it has one bit filled. Any consecutive kills you get with the rifle while the focus is active will fill it again. Headshots and bodyshots fill it and so do no-scopes. Press the reload key to activate it.

When dealing with the tank, shoot at it with the carbine until the meter fills, activate it then smack with with the bushwacka (but you better have the melee's hit speed maxed for that).

NOTE: there's a weird bug that can happen sometimes where you would shoot at anything with the carbine and the meter would not LOOK filled. You can still activate it so don't trust the meter.

If the situation gets desperate with the tanks, buying crit canteens and spamming no-scopes on the tank does much more damage than the bushwacka

Lastly, you can actually headshot sentry busters, they have a tiny head hitbox on top of the peak spike as seen here:

Hitting those headshots on the other hand is very difficult and really not worth the effort since the engie should be perfectly able to deal with it.

Instead, keep shooting giants and dealing with meds. If there's reaaaally nothing else to do and you wanna practice your aim then fire away.

Spy

DISCLAIMER: i have to put this here just in case and to be honest. Even tho i've beaten 666 as spy multiple times, this is still my least played class overall, so if anything i say here is wrong feel free to correct me. That's also true for the rest of the guide but specially for spy.

1: ROLE

I know what i said about spy early in the guide but there's still people who're gonna want to play him 'cause they like the class, and that's fine, so i can at least give the best tips and advises i can to help.

Giant killing, that's your job.

Spy on 1v1 situations against giants is excellent and requires much less money investment than demo and sniper. He can even wear down groups of giants if you're good enough. He can also help with his sapper by paralyzing a good chunk of bots and medics (it will only slow down giants tho).

Other 2 uses he has is money collecting in which he ranks as the 2nd best since he can disguise so bots ignore him while he takes all the money. Spy lacks a magnet or any real benefits to picking money unlike scout tho so don't expect much from doing it besides helping the team.

Lastly, he draws the most aggro of all classes. If you uncloak and remove your disguise in the open EVERY ROBOT NO MATTER WHAT YOUR TEAM MATES ARE DOING TO THEM will shoot at you. This will become important for a strategy i used on the 2nd half of the wave.

2: WEAPON RECOMMENDATIONS

Primary:
-L'etranger: it's an excellent support tool to aid your escape situations and to make sure you're able to do so more often. Not only it'll extend the duration of the dead ringer (which doesn't matter much really) but you can also shoot a couple of times at a robot to have it back up again.
-Revolver (stock): good for damage and reliable.
-Diamondback: if you're a particularly aggressive spy, run this revolver and unload those crits later.

Melee:
-Stock: best choice for starters into the class. No penalties or anything, just straight up good performance.
-Conniver's kunai: health cut to 70 in exchange for overhealing up to 210 with each backstab. It's a very risky knife to run but a very rewarding one was well (specially on the 2nd half since your job on the 1st one is to kill giants)
-Big earner: HP cut to 100 but grants you a speed boost with each backstab. Excellent if you're confident in chain killing.

Cloak:
-Dead ringer: your life savior during difficult situations and to run from the giant if it turns to you.

Sapper:
-Doesn't matter (for this mission at least, more on that later)

3: UPGRADE RECOMMENDATIONS

Giant slayer:

Your knife's armor penetration and hit speed are a must. After that, max crit and fire resistances, then max movement speed. Once the pyro/scout/demoknight part comes, refund the fire resist and invest into blast and bullet resist)

That should do well enough for the first half, upgrade more speed and sapper if you wish.

Harsh bait:

During the 2nd half if you really insist in not doing the "retry console" trick then here's what you can do. Unspec all your points from armor penetration since there's no more giants and send them all to the sapper. By this point you should have resistances and speed maxed out so on top of that and the sapper, get health on kill for the knife and max out the revolver.

No really, all revolvers are extremely cheap to upgrade to the max.

After that, buy uber canteens.

4: STRATEGY

Giant slayer:

Your main job is to clear all giants asap. Be sure to not let yourself get killed. Giants (except for medic) will always end up turning around to look at you by the time you land the 3rd backstab (note: you need 4 to kill a giant) so after this you can do 1 of 2 things:

1: dead ringer out, disguise, wait for them to ignore you again and go get the kill. Rinse and repeat with all of 'em.
2: circle around the giant until you land the last backstab. Some spies can consistently run around the giant and finish the job in one go. That's why movement speed is so important for spy.

While there's no giants, sap some groups of bots or collect money.

Harsh bait:

Here's where you're gonna need to play very aggressively if you want to help as spy during an entire half of the mission where he's useless. There's no giants, no medics (except by the very end), just regular robots that also happen to be charged with crits.

You need to disrupt the robot's advancement in any way you can including using your own aggro capabilities. Spam sappers left and right on groups of bots, get any cheeky kills with the revolver, attempt even to chain backstabs if you feel confident enough, and when the last group comes GET THOSE MEDICS. As many as possible. I know it may be a slow process due to the fact that they're all scattered and the heavies can shred you even at max resistances, but hey, you gotta do what you can, you chose to play as spy this far.

In case of emergency and your team is being overwhelmed and really needs a window of opportunity to deal with the bots, get uber canteens and run in the open uncloaked and without disguise. Have every active robot shoot at you. When you're close to dying, use the uber canteen and so long as you're still being shot at, keep using them until either they're all dead or all 3 run out.

It doesn't matter if you're being pinned against a corner by 3 heavies, so long as they're shooting you and not your team mates.

Money spy:

If you wish to help the team get money, then don't go in with a similar mindset to scout. Don't charge in because you're not nearly as mobile as scout is and also not as resilient to damage. Wait for the kills to happen, make sure the money is not right in front of more robots and pick it. Just because robots ignore you doesn't mean you can't suffer from collateral damage while they're attacking someone else.

NOTE ABOUT THE SAPPER: this one bit is irrelevant to wave 666 but i still wanna include it just to share the info.

The red tape recorder is actually spy's best sapper in mvm. Both perform exactly the same in nearly every situation except when dealing with the engie bots. If you sap the engie's teleporter with the RTR then the engie will completely ignore it, allowing you to get the engie and let your mates know of an easy sentry kill.

Final remarks on classes.

Bloody hell this guide has been long.

NOTE ABOUT WEAPONS: while it is true i recommended exclusively meta weapons for this guide, a lot of people may not have some of these weapons or may even use completely wrong commonly used ones thinking they're good, when in reality they're trash or underperform.

I'll briefly cover some of these commonly used examples:

Scout:
-Force A Nature: remember what i said about knockback on pyro? same applies here. Don't use it.
-Wrapped assassin and cleaver: bleeding sucks in mvm. It's worthless.
Atomizer: it's a very solid utility tool to help your movement in case you don't have a Fan O War

Soldier:
-Black box: can work just fine if for some reason you don't wanna use stock.
-Cowmangler: it's not precisely BAD but in mvm you REALLY need soldier using crits and the cowmangler doesn't have that
-Direct hit: no, the extra damage won't make it do more damage than other rocket launchers when you buy all damage upgrades. It's awful.

Pyro:
Degreasser: garbage. Worse than stock. You're not here to combo pyro.
Thermal thruster: it is actually not that bad as a utility tool but only use it if you really don't have the gas, flare gun or detonator.

Demo:
Quickie bomb launcher: it's bad. Use stock. You can spam better with it without cutting your damage.

Heavy:
Tomislav and natasha: both garbage, never use them. You're better off with stock.
Other lunchbox items: the chocolate bar and the banana are not precisely bad so if for some reason you don't have the sandvich or steak then you'll be fine with those.

Engineer:
-Shotguns: while they're not bad for self defense if you really lack a rescue ranger or a widowmaker, just don't spend points into them.
Pomsom: i need to be fair with this crime against nature of a weapon: it has ONE use. When the giant medic/heavy pair come, shoot at the medic with it so it doesn't pop uber 'cause of the weapon's uber drain mechanic. And even then why in god's name would you use this over the RR or WM but whatever.
Other wrenches: lack any real upside or have too many downsides
Gunslinger: remember my entire rant about the disposable sentry? well yes, this is "disposable sentry: the item:" SO NO. DON'T USE THE GUNSLINGER.

Medic:
Vaccinator: if you REAALLY hate the stock medigun for a deep sense of contrarianism and hatred for the meta then this one is actually not that bad to spam revives so use 'em to your hearts contempt, you're still gonna underperform tho.

Sniper:
-Bazaar bargain, machina and stock: pretty good picks if you don't have the hitman's.
-Huntsman: Yes i've beaten wave 666 with it, no i still wont recommend it for new players until they get good enough to do meme runs of this mission. Don't use it.
Classic: throw it in the trash.
Cozy camper: not bad actually but you wont be helping your team with other ways besides giant killing so yeah.
Razorback: don't.

Spy:
-Spycicle: you feel like losing your knife mid-stab? no? then don't.

NOTE: i've heard of a bug or something involving the spycicle in which if you have your sapper in hand, use the sapper then go to the knife, even if you get set on fire, the sapper will take the knife's cooldown and you're still gonna be able to backstab and attack with it, while also having afterburn immunity. I can't confirm this so i'll place this disclaimer just in case.

IN CASE YOU'RE A FRESH INSTALL AND HAVE EVERYTHING STOCK

First off: why would you even attempt at playing a hard mission like this? play coaltown, decoy, mannworks on normal difficulty. Learn the basics, get a grasp of the game.

Second: if you feel particularly masochistic then these are the classes you can use full stock and still perform well:

-Soldier
-Pyro
-Demo
-Heavy
-Spy

The end.

Man this has been a long trip but i hope it was worth it to the uh...2 or 3 people who're gonna be reading till halfway through and get bored.

Still i had fun making this guide, i made it 'cause I've played wave 666 an insane amount of times, beaten it as every class and some sub classes (bowman, demoknight, combat engie). I love the idea of giving us tons of money to get upgrades and still face a difficult challenge.

Wave 666 can only be played in pubs so you'll most likely find newbies or people who picked the wrong difficulty to learn the game. Still, if they enjoy pain then hopefully this guide will allow 'em to do better.

Why did i make this guide to begin with?

Spite.

I'm leaving it at that with no further context.

Image credit and misc stuff.

While i used lots of images i captured myself for demonstration purposes and showing I did use others that belong to other sources. Here ya have 'em:

Scout milk and fan thumbnail and briefcase with money:
https://www.youtube.com/watch?v=ZETxbACoOwA&ab_channel=PieRow
https://www.reddit.com/r/tf2/comments/iunbzw/how_it_feels_to_play_scout_in_mvm/

Air strike soldier
https://www.reddit.com/r/tf2/comments/3ga02o/airstrike_in_mvm/

Pyro gas and airblast:
https://www.deviantart.com/bielek/art/MvM-Pyro-vs-Demo-bot-425544524
https://www.youtube.com/watch?v=U1nCeyk-tOQ&ab_channel=FireGlassFireLass

Heavy:
https://www.youtube.com/watch?v=beqM4CxARIk

Medic:
https://www.reddit.com/r/tf2/comments/68hrj1/the_colossal_giant_sfm/

Sentry buster's hitbox:
https://steamcommunity.com/sharedfiles/filedetails/?id=124646903

Spy:
https://www.youtube.com/watch?v=D39XH0dgigE&ab_channel=MrPaladin

Rest of images are official sfm and artwork ones from Valve.

EDIT LOG:

19 of April 2024: been a while but after seeing the light, yes, the quickfix is awesome for shield spam. Edited the sections mentioned and added it to the list of recommendations.

[Flakker]

I do understand the usefulness of both vacc and quickfix, but in 666 i'd argue that since everyone can make themselves more resilient much more easily due to the immense money influx, using a medigun that makes your allies "spongier" isn't as useful when they can already be like that, even from the start.

Stock and kritz on the other hand offer a straight boost to something you could only otherwise acquire by dumping your life's savings into canteens.

[Dispentryporter]

I don't know why you say Medic will underpeform with Vacc or Quick-Fix, they're both about as good as Stock. Hell, I'd say Quick-Fix with its fast shield charge is even better than Stock.