No One Left Behind

This is how you can save every character in the "Suicide Mission"

This guide by nature contains SPOILERS. Take care in reading this guide, as this could be considered meta-gaming.

There is also a visualization of all of the possible deaths and survival on an imageshack file.

Before you enter the Omega-4 Relay

Make sure that:

• All squadmates are loyal
  
• All critical Normandy upgrades have been completed

Reaper IFF

Mission Checkpoint: You should complete all available loyalty missions before starting this mission.
After you complete the Reaper IFF, when the "Normandy Ambush" sequence depends on how many open loyalty missions you have left.
Assuming you decided to activate Legion:

• If you have 1 or more loyalty missions left, you will have time to complete 2 missions.
  (For reference, I was able to bring Legion to Tali's mission and still complete Legion's mission.)
  
• If you have completed every mission, Legion will give his loyalty mission immediately or the "Normandy Ambushed" sequence will begin once you use the galaxy map.
  Before you use the galaxy map, Kelly should warn you that Legion wants to talk to you. Talking to Legion will extend the time to complete his loyalty mission.

Normandy Ambushed

EDI will warn you that the next mission will require the shuttle. This is the sign that the sequence will begin. After completing it with Joker, the rest of the crew will be taken by the Collectors and how soon you start the Sucide Mission will determine how many survive.

Normandy Crew

Saving the crew is not required for this achievement., but can add on to "Mass Effect 3".
Crew will die if you complete any missions / assignments after the Normandy is attacked

• 0: All Normandy Crew will survive
  
• 1 - 4: Half the Normandy Crew will survive
  
• 4+: Only Doctor Chakwas will survive

Loyalty Missions

After you complete Horizon, Kelly Chambers will mention that certain squadmates want to talk to you, opening their loyalty missions.

Jacob: The Gift of Greatness

Location: 2175 Aeia (Rosetta Nebula)
Help Jacob discover what happened to his father and the crew of his ship.

Miranda: The Prodigal

Location: Illium
Help Miranda save her sister Oriana from her estranged father.
Loyalty will affect her survival in Mass Effect 3.

Jack: Subject Zero

Location: Pragia (Nubian Expanse)
Help Jack recover her memories from Pragia and then destroy it.

Mordin: Old Blood

Location: Tuchanka
Help Mordin rescue and discover what his protege Maelon was doing on Tuchanka.
Your choice at the end of this mission will have a major impact in Mass Effect 3.

Grunt: Rite of Passage

Location: Tuchanka
Help Grunt complete his rite of passage to adulthood on Tuchanka.
Loyalty will affect his survival in Mass Effect 3.

Garrus: Eye for an Eye

Location: Citadel
Help Garrus find the turian who betrayed his squad on Omega.

Samara: The Ardat-Yakshi

Location: Omega
Help Samara find her murderous daughter on Omega.
Failure: Failing to draw in Morinth will allow her to escape.
Your choice at the end of this mission will have a minor impact in Mass Effect 3.

Tali: Treason

Location: Migrant Fleet (Valhallan Threshold)
Help Tali investiage why she is being charged with treason.
Failure: Choosing to reveal Rael's evidence will traumatize Tali.
Your choice at the end of this mission will have a major impact in Mass Effect 3.

Thane: Sins of the Father

Location: Citadel
Help Thane find his son and stop him from making the same mistakes he did.
Failure: Taking too long will allow Kolyat to escape.

Legion: A House Divided

Location: Heretic Station (The Phoenix Massing)
Help Legion combat the geth heretics and their reaper virus.
Your choice at the end of this mission will have a major impact in Mass Effect 3.

Zaeed: The Mercenary

Available by DLC (Cerberus Network) and can be completed at any time.
Location: Zorya (Faia System)
Failure: Choosing to save the workers and failing to persuade Zaeed will prevent him from listening to you. You can also leave him to die if you complete this after the suicide mission and choose the save the workers.
Loyalty will affect his survival and have a minor impact in Mass Effect 3.

Kasumi: Stealing Memory

Available by DLC (Kasumi's Stolen Memory) and can be completed at any time.
Location: Bekenstein (Serpent Nebula)
Help Kasumi recover her partner's graybox and its secrets.
Loyalty will affect her survival and have a minor impact in Mass Effect 3.

Normandy Upgrades

Before entering, make sure you have all 3 critical Normandy upgrades, otherwise squad members will die while making the crash landing.

Kinetic Barriers

* Talk to Tali
* Cost: 15,000 Palladium
This will keep the engine core steady on entry to the Omega-4 Relay. Otherwise, the engine core will explode, causing an explosion in engineering and killing 1 squad member.
Kasumi, Legion, Tali, Thane, Garrus, Zaeed, Grunt

Heavy Ship Armor

* Talk to Jacob
* Cost: 15,000 Palladium
This will protect the structure of the Normandy during an ambush in the Galaxy core. Otherwise, the attack will break through the armor and immediately kill Jack, unless she was with Shepard to deal with intruders.

Thanix Cannon

* Talk to Garrus
* Cost: 15,000 Platinum
This will successfully destroy a Collector cruiser guarding the Collector base. Otherwise, the Normandy attacks at close range, and the cruiser weapons will break through the armor and impale 1 squad member.
Thane, Garrus, Zaeed, Grunt, Jack, Samara/Morinth

Act I: Enter the Collector Base

After the Normandy enters the Omega 4 relay, the Normandy will make a near-crash landing.
A squadmate is ideal only if they are loyal. Otherwise they are not ideal.

Technical Specialist

Your specialist will infiltrate via the station's vents to bypass the defenses and doors then open the central gate for the rest of the squad. You want a squadmate skilled in tech.
Ideal Squadmate: Tali, Legion, Kasumi
Not Ideal: Anyone else or nonloyal. Your specialist will be shot in the face as they try to close the gate.

Foreshadow Hints:

• Jacob will volunteer, but Miranda will mention that he failed to stop the Lazarus Station mechs fast enough

Fire Team Leader

Your team leader will lead a distraction team while you infiltrate the Collector base. You want a squadmate with skilled leadership
Ideal Squadmate: Garrus, Jacob, Miranda
Not Ideal: Anybody else or nonloyal. Your team leader will get your technical specialist killed.

Foreshadow Hints:

• Tali's teams on Freedom's Progress and Haestrom were wiped out, with only one or no survivors.
  
• In a story, Zaeed will mention that he was the only survivor during a mercenary mission.

Act II: The Long Walk

After the team infiltrates the collector base, the team will regroup.
With searching, the team will discover pods of people being decomposed.
If you entered soon enough, only a colonist is consumed and your crew survives.
If you took too long, Kelly Chambers is consumed along with half or all of your crew, with only Doctor Chakwas surviving.

A squadmate is ideal only if they are loyal. Otherwise they are not ideal.

Biotic Specialist

Your specialist will create a biotic shield to protect you and your squadmates from the Collector swarms. You want a squadmate skilled in biotics.
Ideal Squadmate: Samara/Morinth or Jack
Not Ideal: Anybody else or nonloyal. One of your squadmates will be carried off by the Collector Swarm.

Foreshadow Hints:

• Jack is described as a biotic maniac when you recruit her.
  
• Samara is an Asari Justicar with years of experience in biotics.
  Users have also pointed out that parts of "The Long Walk" musical theme are in Samara's musical theme.

Fire Team Leader

Your team leader will lead a distraction team while you infiltrate the Collector base. You want a squadmate with skilled leadership
Ideal Squadmate: Garrus, Jacob, Miranda
Not Ideal: Anybody else or nonloyal. Your team leader will take a fatal shot as the gate closes.

Foreshadow Hints:

• Tali's teams on Freedom's Progress and Haestrom were wiped out, with only one or no survivors.
  
• In a story, Zaeed will mention that he was the only survivor during a mercenary mission.

Normandy Escort

Your escort will take any Normandy crew survivors to the Normandy. Your squadmate will be unavailable for the rest of the Suicide Mission.
Ideal Squadmate: Any loyal squadmate. (Mordin strongly recomended)
Not Ideal: Any nonloyal squdmate. Not choosing an escort will get the Normandy crew killed. A nonloyal escort will die while escorting the crew to the Normandy.

Act III: The Final Fight

After a successful fight and infiltration of the base, the remaining collectors will attempt to stop the team from progressing. You have the option of two squadmates and the rest will distract the collectors while you fight your way to the final boss.

The Final Fight

Ideal: Loyal squadmates that are bad at defense (Tali, Mordin, Jack, Kasumi)
You can take any squdmates to the final fight, as long as the distraction team has a strong defensive score of 2.0 or higher.
Not Ideal: Any nonloyal squadmates. They will die after the base begins to collapse.

The Distraction Team

Survival of the remaining squdmates depends on a "defensive skill" or "squad rating". A squad can easily survive with at least two squdmates with a strong defense (Garrus, Zaeed, Grunt).

Every squadmate has "defense value" to contribute. Add the points value for each squadmate and take the average of how many in the group.

Name	Loyal Score	Nonloyal Score
Jack Kasumi Tali Mordin	1	0
Thane Legion Samara/Morinth Jacob Miranda	2	1
Grunt Zaeed Garrus	4	3

If the average is 2.0 or greater, the entire team will survive regardless of size or loyalty.

Otherwise:

• 5+ Teammates
  • Avg < 2.0: 1 Death
    
  • Avg < 1.5: 2 Deaths
    
  • Avg < 0.5: 3 Deaths
• 4 Teammates
  • Avg < 2.0: 1 Death
    
  • Avg < 1.0: 2 Deaths
    
  • Avg < 0.5: 3 Deaths
    
  • Avg = 0.0: All dead
• 3 Teammates
  • Avg < 2.0: 1 Death
    
  • Avg < 1.0: 2 Deaths
    
  • Avg = 0.0: All dead
• 2 Teammates
  • Avg < 2.0: 1 Death
    
  • Avg = 0.0: Both Dead
• 1 Teammate
  • Avg < 2.0: Dead

Any nonloyal squdmates will die first. After that, squadmates will die in this order: Mordin, Tali, Kasumi, Jack, Miranda, Jacob, Garrus, Samara/Morinth, Legion, Thane, Zaeed, Grunt

[Snowman]

very helpful thank you very much!

[MrGrumpsman]

@SerWind
If you do legion's loyalty mission immediately after the IFF, it's business as usual. Accessing the map after that will trigger the collector abduction on the normandy, so as long as everything else was done before IFF, you're golden.

[SerWind]

So if you do Legion's loyalty mission after getting him, half the crew will die? I did the suicide mission without Tali loyal and she survived. Pretty sure you just can't send non loyal people on any specific tasks or bring them with you during the final fight.

[Alpha Lee]

i managed to have everyone survive my first playthrough, getting the ship upgrades simply cuz i thought they would be good to have. I also used legion for the unlocking, who survived. He only dies if you use a nonloyal member for the fireteam leader

[rich55]

Well, Grunt and Legion died, even tough they were both loyal with me

[DoubtingThomas04]

This guide also incidentally happens to tell you how to let all squad members die. Just saying.

[Aeterna Nox]

Okay. Collector heavy beam rifle is the meta here. Easy.

[Aeterna Nox]

Love your guide. Helped me I think three or four times. But man. Playing the Husk section in act 2 as an Infiltrator is living hell on highest difficulty. Squadmates simply won't tank long enough so I could recover.Hey, @SilentMarine, do you have any tips?

[The Fairy Love Sniper]

Kinda wish more missions were as serious as this were it took planning. Then again. i would be pissed if every side mission was a suicide mission

[The Fairy Love Sniper]

This guide has saved my ass so many times on so many playthroughs.