Tips for Fairy Duo fight?

[Flariz]

Okay so its Impossible Fairy fight time, and I came to the realization this fight is probably the one that I know almost nothing about- even when I defeated them on BEX back then it felt mostly luck and couldt consistently beat them even after I already beat them 1 time.

This fight is quite a bit different from the others... Almost nothing Erina can do is useful... whats the best way to do DPS in this?

I already have an idea of what Item/Badge setup I should use. Ribbon Badge is obviously made for this fight, but uh...
Whats the best shot for dealing damage?

Currently I alternate between spamming Green Charged shots, and when the MP is low, I switch to spamming Rainbow common shots- because I heard theres a damage penality with Ribbon Badge if your mana is below 50%.
So Green Charged when its above 50%, and when its lower I switch to Rainbow Common.

I also try to use Rainbow Charged whenever I can but its not that useful here, not to mention quite hard to land the shot.

Super Carrot spam whenever applicable, too.

I also try to manage the enemies that spawn for the Healing they give. Try to not kill them all too fast so I can recover later... though sometimes they kill themselves without me doing anything..

Everything is like a 3 hit kill, even with DEF Trade badge lol. Theres still a difference between ATK and DEF Trade, I do survive a tad longer with DEF.

So far my best is both Fairies at about x30 HP bars left. Theres still quite a lot left. And I seriously hope their Cut-In attacks arent insane. They already were pretty crazy on BEX.

[Remin]

I haven't fought them enough to say for sure either, but I guess purple seems okay too? The basic shots can hit them both if they're on one side, and sometimes the charge since it's made of multiple projectiles as well.

Originally posted by Flariz:

because I heard theres a damage penality with Ribbon Badge if your mana is below 50%.

Hnnnngh XD Of all the times I brought it up, I don't think I'd ever once named 50% as the starting point for the reduction, just that there's another damage penalty at that point. It takes an extra chunk out of the damage when you've gone below that amount. 75% mana is when gradual damage falloff starts. So ideally you don't want to go below 75%, but it's not too bad until 50%.

I also wonder how effective that "Super Bunny Whirling Drill Attack" I talked about in the Mid-game Questions thread would be… I think most of the time they're surrounded by bullets… But at the very least I imagine it would be a good revenge move after taking a hit.

For those wondering what that attack is in case you haven't been keeping up with that other thread, the step-by-step process is Quick Dropping into a Bunny Whirl into the bottom of an airborne boss, then down drilling immediately after the bounce. That allows the down drill to hit a lot more than normal thanks to the upwards bounce momentum of the Bunny Whirl. Simple to explain, but difficult to pull off, haha. Can even finish it with a point-blank green charge.

But yeah, since these fairies aren't stunnable as far as I'm aware, they might move away in the middle of the drill as well, which would lower its viability.

P.S. I've been meaning to get back to the other threads, but I decided to take a bit of a break to play Mordhau, a totally different kind of game from Rabi-Ribi that recently came out. A couple days ago I'd actually 99% finished writing another response to your rainbow egg thread, but there was/is one more tiny thing I wanted to test, which is when I started the break by going to sleep haha. And speaking of sleep, time to do just that!

[Flariz]

Purple shot was what I used on BEX and I was considering it here as well, however since I have so many Easter Eggs (60+) I figured Rainbow Shot is probably better- even leaving Charged out of the equation. Its common shots are buffed, too (... I kinda wonder if its Boost also does more damage?).

interesting new thing I learned about this fight:
Whenever Ribbon Boosts, the Fairies get Defense Down...
This is oddly specific behavior but I guess it may have to do with the fact it IS their fellow fairy friend actively attacking them now instead of just Erina, and they just let their guard down because of it, or something along these lines...

Anyway. This means that ideally when Ribbon uses a boost (I think any of them will proc Defense Down on them), Erina should be hitting them as hard as possible... But as already stated, her options are very limited on this fight. Super Carrot Spam aside theres just nothing much else to do that I can think off. Cool discovery, if anything, but ultimately it doesnt means much.

Really, probably the most valuable info would be to know whats the ideal shot to deal the most optimized damage on this fight. Is Blue even worth it? It seems kinda hard to shot them with it- and if you sre going to take the chance to use a non-homing shot, I would go Rainbow Charged, honestly.
(Heck, considering I am in the low 100-150ish HP nearly the entire fight, maybe Carrot is good?)

Best Boost, too. I cant ever decide which one is best. Blue is good, but single target. Red or Yellow may be used for Super Carrot Spam- but then again, Rainbow is also good for that due to Amulet Cut, plus Defense Down is already active on the fairies due to the boost, so its still good damage either way.

Its really too bad the mana damage starts to be lower as soon as 75%... I already thought it was kinda underwhelming it did no real damage past 50%. And now you tell me, that its not quite worth it as soon as 75%?

At that point I question myself why I am even using the Ribbon badge if its gonna be like that, honestly. I am ALREADY using both Mana Badges and the -HP +MP one (Ribbon Mana is 450), and it doesnt take long to drop to 50%, so 75% is just... I will try to give it more chances but damn... Ribbon badge why do you keep being underwhelming to me. First you dont shoot when doing Penta Hammer, and now this :/

I may as well activate Bunny Whirl. Maybe its damage will be decent. Unfortunally theres no way I am doing that super combo, not in this already chaotic fight where you die in literally 3 hits and you also have to manage MP for Ribbon Badge as well as dodge and manage enemies for HP and try to make perfect shots with Rainbow Charged and... uh yeah... You get the picture.

By the way, my new PB is Pixie at like x7 HP bars (Survived her Cut-In) and Lillie at x30. My greatest fear is Lillie's Cut-In attack. NO idea how to dodge that, even on BEX, let alone whatever mounstrosity Impossible does with it.

[Remin]

Well, the badge is still worth utilizing between 50-75% mana, but more so if you're trying to squeeze out damage before the boss vanishes/goes out of reach (e.g. Irisu a lot of the time). It's a slow damage falloff, so it's not going to instantly do terrible damage a bit below 75%. And the badge doesn't stop working during the penta combo, it just gets interrupted a lot. Which isn't really a big deal when you can recharge within like half a second due to the increased clocking speed from the penta. The firing speed is increased because of that too, which usually makes up for the interruptions anyway.

Though in the first place, it's arguable that the Ribbon Badge is more about having constant and much stronger ranged damage for when you can't get close, rather than for close combat. Except point-blank green charge spam. That's always amazing & satisfying when bosses are in the middle of an attack. And red spam for keeping SP up during a continued penta combo, but the penta gets quite weak and draining eventually, so I'm not sure how effective that is overall (the red explosions will constantly be doing damage though, which aren't affected by the mana penalty by the way).

But yeah, if rainbow charges are all you plan to use, the Ribbon Badge is gonna be mostly useless. Can't rapid-fire rainbow charges (though I wonder if it's possible if you ate a donut right after a first shot? Guessing they'd need to be unstunnable even if it can, to prevent the 2nd hit from probably being a dud due to hitting in the same stun that'd be caused by the 1st rainbow charge). There's also the mana penalty for things that aren't red/orange post-hit damage, which ruins any plans to spam charge magic after a recent rainbow charge.

Speaking of orange, I think a good amount of its damage comes from the spawned carrot bombs, so you'd probably be better off not using it in this fight. 150 health also sounds a bit high for orange to be comparatively good… I remember experimenting with it ages ago, though I don't remember the numbers very well; for some reason I wanna say 32% health or so was when either charge or basic shot damage started getting increased? Don't remember which… But basically it's still as super weak as it normally is until around then I think.

By very convenient coincidence on the topic of the Ribbon Badge penalty, when I tried to search a Notepad file of mine for "orange" to see if I wrote about its damage, I saw an old steam comment of mine that I'd copypasted into it mentioning my observation of a video that the extra penalty at 50% mana was a loss equal to about 15% of your max damage. After a quick search for the thread, looks like it's here, specifically the last two thirds of my P.S. paragraph are where I mentioned it. The thread's also about as old as I expected (2.5 years old haha). Also as expected, my love for point-blank green charge shots was still running strong even back then judging by my last post in that thread XD Heck, I apparently still mentioned sleepiness, which I realize I've been doing in a lot of my posts lately. And I plan to do that again here, since I'm about to go to bed XD (I read/wrote this at the end of the day)

Originally posted by Flariz:

Purple shot was what I used on BEX and I was considering it here as well, however since I have so many Easter Eggs (60+) I figured Rainbow Shot is probably better- even leaving Charged out of the equation. Its common shots are buffed, too (... I kinda wonder if its Boost also does more damage?).

interesting new thing I learned about this fight:
Whenever Ribbon Boosts, the Fairies get Defense Down...

Basic purple's probably still more total damage if you can hit both at the same time. It also does more damage to enemies the closer to the edge of it they are (or point-blank, in which case the highest damage bullet takes priority, which is the outer-most shot).

Didn't know that about the boost reducing their defense… Goes to show how rare it is for me to use boosts XD I wonder if I used it when I beat them originally, which I think I've actually only done once… I probably did use it but just forgot. Good to know either way!


So yeah, I dunno if the percentages I mentioned in this comment are still accurate even now, but it might be worth it for you to experiment with them. As for me, it's time for sleep!

[Juno Brier]

What worked for me was switching between blue boost for damage (and defense boost) and purple or rainbow uncharged shots to build up boost again (and of course super carrot and amulet for damage too). Of course, I don't have any math to back me up, but the common factor here is attacks that require little to no aiming to hit those tiny distant hitboxes so I could focus on dodging.

Actually since my strategy above didn't make use of charge shots at all, I was able to safely remove the Ribbon badge since the charge shot spam is its main draw. Again, no math to back me up in regards to other benefits.


And here's my advice for Lilli's mega-laser attack: Use the quick drop to speed up your horizontal movement. And just keep moving.

[Flariz]

Hmm I am not very convinced on Blue Boost mostly because it can only target 1 at a time... I think Boosts may be better spent on Rainbow or maybe Yellow for Super Carrot spam... But when I have no Amulets to do that, maybe Blue is best, but then again I rather have Ribbon ready to shot and spam Green Charged or maybe Yellow or...

Aahhhhh man this fight is so hard to figure out! Honestly...
I have reasons to believe this is the hardest fight in the whole game on a Impossible w/o Consumables or Buff run. (EriNoah has checkpoints so I really doubt it will be as bad)

I keep trying all different combinations I can think of. In the end, I am starting to think there is no definitive "Best" shot/magic for this fight. I think its more like, each specific attack pattern has a Best shot, but it depends on the attack.


Yellow Charged Spam is best when they are both somewhat together.
Blue for when you can only reasonably shot at one for an extended time- and you do NOT need to jump.
If they are in a fixed place but you need to jump, Red charged works better.
Green Charged for when they cant be easily hit by forward shots; also in Green Charged spam vs Purple Shot, it *seems* like Green spam is a tad stronger, but its harder to control (You need to position yourself properly AND actively manage your MP so its always above 50-60%). I also think Purple is a tad faster at building BP, though I rarely want to get BP faster, still something to take into account.
Carrot is useless, dont bother with it in this fight.

Managing the Bunny mobs that spawn during the fight correctly is ABSOLUTELY ESSENTIAL

First off, they love to spawn and drop on your head. If you are at 1HP already, you should already be doing a hammer attack-ANY attack- so they dont kill you. Then you also dont want to kill them all too fast, you have to keep them alive and thats harder than it sounds in the middle of all the chaos, you can kill them accidentally (Ribbon homing shots and a Single Amulet usage can kill them), or also they can kill themselves by dropping off the stage- thankfully they can still heal you even if they die by themselves, but it can still backfire.

Another possibility is to use them to get the X2 damage sliding modifier, and use a Rainbow Charged on the Fairies. Aditionally, remember when I said whenever Ribbon Boosts, the Fairies get Defense Drop debuff?
You can sort of abuse this: When you have x2 sliding modifier, Shot the Charged from a distance, then activate Rainbow Boost: With good timing, you will hit one of them with the Rainbow Charged while Defense Drop is active for them, dealing MASSIVE damage (I think they lose like x20 HP bars or so).

Of course, this strategy literally needs Full MP, at least half BP bar, Bunny Mobs to Slide off for X2 damage, not missing the Charged Shot, and, of course, you have to do all of this while dodging (meh, in reality I just tank a hit for this).. And, although the damage is pretty amazing, at the end of the day its only aganist 1 of the 2 fairies, and all the time spent into doing this could have been spent in just shooting, so the DPS burst may not even be worth it.

Not helping matters is that these 2 have SO MANY attacks... Irisu was the hardest fight before these two, but at least she followed a fixed pattern. You knew what to expect, and thus could eventually (after a LOT of practice) deal with the ridiculous Impossible patterns.
Here it just feels luck based. I feel like they have one of- if not THE- biggest attack pattern pool in the game. They must have like 20+ different attack patterns.

There is one particular pattern I always though was quite silly even on BEX- the one where Blue and Yellow lines/lasers follow you. What the heck is this? Doesnt seem possible to dodge. At all. It kills runs. Even on BEX it was a pretty major run killer.

I wish I could make use of your advice on Lillie's cut-in attack... But I havent reached it yet after 2 days of attempts. Also, I think they changed how the out of bounds work? You just used to respawn at around the center of the screen at 1HP- and you could abuse this for free iframes because it couldt kill you. That was something I planned to use for Lillie (just like I did on BEX, lol) but it just launches you upwards and can actually kill you... It wasnt like this before I am pretty sure.

I know I cant complain too much about the difficulty of an unstable game mode with additional conditions on top of it, but much of what I said applies to BEX version as well. I guess I just dont know how to deal with this fight xD its too different from all other bosses.

Even when watching how other players do this fight, everyone just uses different shots. There doesnt seem to be an "optimal" way to do this.

[Shade]

If you'd like another opinion:
MAX Blue Boost worked fine for me on BEX Incredibly Intense; I don't remember ever having much trouble with the fairy duo.
But then again it's worth noting I use Blue Boost for pretty much everything boss-related - my entire playstyle is pretty boost-centered, so what worked for me might not necessarily work for you, especially on an even higher difficulty.
So yeah. Good luck with the fight, in any case!

[Flariz]

I tried.
I tried the Boosting method, however even Blue Boost loses to a really agressive Ribbon thats actively shooting common/Charged shots instead of just boosting.
I even tried it with MAX Bracelet...

But it just takes too long to do its DPS. And ALSO, the shorter iframes really hurt me, I NEED the long iframes in order to survive.
Some of the dodging in these patterns is extremely tight, and the Speed Up buff screws me up, too.

That said, I concluded something new:

Out of all the Boosts, the best for this fight seems to be Rainbow Boost.
It simply deals the most overall damage to the Fairy Duo Iby itself . Its worth noting the damage may or may not be influenced by the 60+ Easter Eggs I have collected.. no idea since I never paid too much attention about Boost DPS until now.

But theres a strong argument about Rainbow Boost being the best for this fight. Aside from damage, it provives Amulet Cut, so you can spam Super Carrots; and those coupled with Defense Drop debuff caused by a boost do some really nice damage, and depending on the attack the Super Carrots may damage both of them at the same time.

The only bad/good thing about Rainbow Boost is that it hits everything on the field, even if it is Off Screen. Good for the fairies; Bad if you want to keep Bunny Mobs alive for healing (And you DO)

Yellow/Red also give you Attack Up but I feel like the boost giving Defense Drop on the Fairies is enough damage already, and I rather focus just a bit on having Amulet Cut instead.

Blue has Defense up... but things hit a tad too hard on Impossible difficulty for it to make much of a difference, I rather bet on more iframes opportunities (Again, Amulet Cut wins)

The other Boosts are useless both Damage and Utility wise.

So, at least now I dont have to worry about using an inefficient Boost anymore. I know Rainbow Boost is best here.


Also, I had the most unpleasant experience with this fight just recently.

ZERO OFFENSE

This debuff... why

You DONT know how frustrating it is to get hit by this near the end of the fight-
It seems like it happens on the last attacks/patterns at random- you get hit by it, and most likely the same hit puts you at 1 HP. Theres Bunny mobs that could help you by giving you more HP right there... and you CANT kill them because of Zero freaking Offense Debuff!
And it lasts what seems to be an eternity...

Theres no Badge to counter this thing either. As far as I can tell its RNG whenever you get a status effect or not, sooo... all you can do is simply hope it doesnt procs whenever you get hit, lol.


For anyone thats reading this and just so happens to want to do Impossible w/o Consumables or Buffs (I am not alone, I know of at least 2 other people): Stop at Irisu. Do yourself a favor and stop at Irisu. Maybe up to Pillar Saya.
These 2 fairies... are something else...


BTW I think the Ribbon Badge helps just enough to be useful, and yet at the same time it is no game changer.

Lilli seems to be a higher level than Pixie (Its also probably the reason I faced Pixie´s Cut-in attack about a dozen of times or so, but I have yet to see Lilli´s, lol), so it may be a good idea to focus a bit more on attacking her over Pixie (?)

[Remin]

Originally posted by Shade:

my entire playstyle is pretty boost-centered

Opposite of me, I almost never use boosts XD

I'm still addicted to another game right now so I haven't gotten around to testing more Rabi-Ribi stuff lately, but just wanted to comment on a few things still:

Originally posted by Flariz:

Yellow Charged Spam is best when they are both somewhat together.

Purple single-charge charges are better if you can hit both fairies (double-charge does no extra damage unlike the rest, unless you count the weak 360° extra attack). It has the highest direct-hit damage of all the regular single-charge charge shots other than probably orange at low hp (unless even that loses; I do feel like I remember a good chunk of orange damage coming from the spawned carrot bombs), and can even hit up to two targets. And the Ribbon Badge can only use single-charge charge shots. However, it might throw off the timing of some of their attacks due to the slowing auras. Definitely the highest total damage when spam hitting both fairies, though.

Originally posted by Flariz:

Another possibility is to use them to get the X2 damage sliding modifier, and use a Rainbow Charged on the Fairies. Aditionally, remember when I said whenever Ribbon Boosts, the Fairies get Defense Drop debuff?
You can sort of abuse this: When you have x2 sliding modifier, Shot the Charged from a distance, then activate Rainbow Boost: With good timing, you will hit one of them with the Rainbow Charged while Defense Drop is active for them, dealing MASSIVE damage (I think they lose like x20 HP bars or so).

Of course, this strategy literally needs Full MP, at least half BP bar, Bunny Mobs to Slide off for X2 damage, not missing the Charged Shot, and, of course, you have to do all of this while dodging (meh, in reality I just tank a hit for this).. And, although the damage is pretty amazing, at the end of the day its only aganist 1 of the 2 fairies, and all the time spent into doing this could have been spent in just shooting, so the DPS burst may not even be worth it.

Yellow or red boosts after firing would be better for the Attack Up buff.

I dunno if Defense Drop is additive or multiplicative. Attack/Defense Up/Down are all additive with each other, but multiplicative on the final damage. Seems like a good fight to test it on since you can directly control when they get Defense Drop.

Slides can hit enemies in the air as well, as long as they're not above the max height of your initial jump. Bunny Strike works the same way.

Also it feels weird to say the sliding boost gives x2 damage… It's technically +100%, which sounds similar, but it's additive (with non-buff multipliers), not multiplicative. So if you were doing 165% total damage from MAX combo and ATK Trade (+40% & +25%), sliding boost would make it 265%, not 330% (it's not 165% x2).

So… Depending on how Defense Drop works (and what its value is, since it can apparently be between 100-300% according to its description; I'll just say 100% for the sake of the following words), it'll either double your final damage or add another 100% to your multiplier. My guess is that it's multiplicative on the final number, but possibly additive with the main damage-altering buffs (Atk/Def Up/Down), judging by how those ones work.

[Flariz]

Originally posted by Remin:

Opposite of me, I almost never use boosts XD

I'm still addicted to another game right now so I haven't gotten around to testing more Rabi-Ribi stuff lately, but just wanted to comment on a few things still:

Same... in fact, this made me realize I use Boosts mostly as a way to complement Erina´s attacks/survival. By themselves, they arent all that good, honestly- And since in this specific fight Erina cant really do much other than Spam Super Carrots in certain attacks... yeah. I believe I am better off mostly shooting normal/Charged.

In short, I believe a Ribbon thats just shooting her normal magics will do better DPS than any of the Boosts could without Erina´s assistance.

Theres a fair point for Boosting though, and that is Ribbon is doing her DPS part completely automatically. You dont have to worry about best shots for each situation and such anymore, you can just focus on Dodging (Personally I would also try to attack with Erina in the meantime, but if you have a more cautious playstyle, I can see it the appeal on it). Unfortunately, just Dodging itself wont work very well on Impossible.. you really need good DPS, too.

Also, I can totally relate to being addicted to another game so much, you cant play/comment on a previous one that much anymore... fun fact: Thats the exact same thing thats happening to me now; except Rabi-Ribi is the game thats the addiction thats "preventing" me from coming back to a previous game series xDDD (No worries though, its all good. Eventually I will find enough time for both!)

Originally posted by Remin:

Purple single-charge charges are better if you can hit both fairies (double-charge does no extra damage unlike the rest, unless you count the weak 360° extra attack). It has the highest direct-hit damage of all the regular single-charge charge shots other than probably orange at low hp (unless even that loses; I do feel like I remember a good chunk of orange damage coming from the spawned carrot bombs), and can even hit up to two targets. And the Ribbon Badge can only use single-charge charge shots. However, it might throw off the timing of some of their attacks due to the slowing auras. Definitely the highest total damage when spam hitting both fairies, though.

Hmm, I will give it a try. I wonder how large the AoE/hitbox for the Purple Shot is, so I could hit both of them at the same time...

Originally posted by Remin:

Yellow or red boosts after firing would be better for the Attack Up buff.

Yeah, you are actually right. I dunno if theres enough time to switch the Boost... even with the pause magic wheel, remember you just shot a Charged Rainbow, which means next to zero MP, which means the Boost will be extremely short lived (Literally 1-2 seconds).

Defense Drop Debuff actually stays active for a bit more than the Boost itself, so its not incredibly hard to hit them while it is active.

But I think your own Boost buffs go away immediately... I will have to test this.

On a unrelated sidenote. I finally learned how to properly quote in this forum xD.

EDIT: New "Progress"
https://i.postimg.cc/fTQ0nPW5/No.jpg

You know, if this attack IS how I am thinking it is..
If its really undodgeable, then...
Thats it. Its over.
The difficulty finally takes its name seriously?
Theres no way to beat this without Consumables.

The Cut-In attack is way too long to simply tank, and good luck having enough Amulets for it lol. Plus I was using ATK Trade, maybe if you enter it with DEF Trade and like 3-4 Amulets but thats just not reasonable...

Jeez why are these two harder than Erina, anyway? Even on BEX, I always thought these 2 were the hardest boss fight in the game (Assuming you fight them following the common order ex No Wind Blessing, Fairy Flute, 5th Amulet and Bunny Memories and all that fancy stuff). Or at least, the most inconsistent of them all- Too many attacks, some a fair bit easier than others, some were dealing DPS is no problem and on others you can hardly hit them...

And the bugs I constantly find in the fight certainly dont help. Theres no excuse for Camera/zoom acting weird and getting stuck in the Air phases glitches.

[johnbeanpotter]

run

[Flariz]

Hmm...
Does anyone know what determines the Bunny mobs spawn?

I have reasons to believe its not completely RNG.
Because I just made them spawn AT Lilli´s Cut-In attack- that could potentially make surviving it doable (Too bad I died anyway because laser got me before I could kill 1, I had 3 AMULETS but I was stuck in that downdrill animation so I couldt Amulet in time, too bad).


At some other attempts, they just eventually stop spawning when they are at around 20-30HP bars left...

But I dont think its actually HP based.

I think they have fixed number of times they can spawn, and depending on how fast you drain the Fairies HP, the later into the fight they will be spawning in.

In the attempt that they spawned in Lilli´s Cut-In, I damaged both of the fairies particulary fast, maybe one of the fastest times. So I think I got something with how the spawns work here.

They ALWAYS spawn at Pixie´s, but usually they stop spawning a little after that.

If I could get them to consistently spawn in Lilli Cut-In, too, then it may actually be doable.

[Ru]

Originally posted by Flariz:

Does anyone know what determines the Bunny mobs spawn?

They will only spawn when an attack pattern starts, and, as far as I know, it can be on any pattern except the last one. They'll always spawn during the fight, but when and how many times they spawn is random. I could absolutely be wrong but I don't think it's fixed at all. Or HP-based, for that matter.

At least, that's the conclusion I came to around a year ago.

[Flariz]

I have got nothing that refuses nor proves what you said. I havent figured out the spawns either, its all speculation... I wonder how they actually work...

https://youtu.be/DWRJd_w6LEw


Oh well, at least its done now :)
I want to thank you all for your tips guys, any help is appreciated!

@Remin: Your input in particular was essential. I ended up using both Purple Charged shot spam for DPS since you said it was the best for when the 2 fairies are together, as well as started applying Red/Yellow boost for the Rainbow Charge shot + Boost combination- really helped to do more DPS and move the fight faster, thanks!

Some other misc things/tips/comments I have to say about the fight for anyone out there stuck at Imp Fairy Duo, just as closure of sorts (I will try to be brief this time dont worry)

*Go Full DPS build. ATK Trade, Crisis Boost, Health Wager, Ribbon Badge all recommended.
*As already discussed Slide for x2 damage + Rainbow Charged Shot + Yellow/Red Boost before it actually hits: MASSIVE DPS on 1 Fairy.
*Probably the most luck-based fight in the game. Depending on attack patterns/bunny mob spawns/whenever Zero Offense debuff procs or not, sometimes you just dont have much of a chance to win...

But the #1 Most important thing is: Good Bunny Mobs management.

Manage these guys well, take care of them, use them to get out of Survival Instinct and abuse the iframes when getting hit in order to attack the Fairy Duo!
Always be ready to hammer them as they spawn, otherwise they may spawn on top of your head and kill you :/ (What the heck is up with this by the way, they shouldt be able to just spawn on top of you like that to begin with, honestly...)
They are also useful to recover MP with the green shot ridiculously fast- so you can keep shooting more Rainbow Charged shots/Purple Charged shots

Also, Lilli´s Cut-In is FAR from impossible to dodge. It is very nerve-racking though.

IMHO they are the hardest fight in the entire game on a Impossible run (That is, Chapter 1 to Chapter 10- BNA bosses are excluded from this).

All of this probably can be applied to BEX and lower, too? Well theres probably no need to go Full DPS there, but... it could probably make the fight take a lot less than it normally does, so theres that to consider I guess. Its probably a better idea to play it safer though.