Mass Effect 2
The endings get a bit more complicated in Mass Effect 2, as the outcome will depend on several things: your preparations, combined with the appropriate decisions during the suicide mission, and your final choice regarding the Harvester station.
So we are going to cut this into several sections.
Survive the suicide mission
Mass Effect 2's final mission will kill your companions one by one if you make the wrong choices, or if you haven't completed all of the Normandy SR2 upgrades.
If all your companions die, Shepard also ends up passing away at the very end, which can be considered the worst possible ending.
In this specific case, you will not be able to use this save to play Mass Effect 3. The dead companions and their dedicated missions will obviously be absent in Mass Effect 3 if you just lose a few on the road.
So here's a step-by-step guide to helping everyone survive and get that perfect ending, although you're free to make the wrong choices on purpose for an alternate ending!
Improve the Normandy
By talking to the various crew members between the Harvester mission and the Harvester Wreckage mission, you will unlock special dialogue options with Tali, Garrus, and Jacob, which will unlock new special upgrades for the ship.
In the Normandy upgrade interface, you need to make the possible upgrades to the ship in order to avoid some crew member deaths. Kinetic barriers, the Thanix Cannon, and heavy hull armor are the most important.
Loyalty missions
You must build your reputation with all the crew members and fulfill their missions of loyalty in order to secure their survival as well as their performance. Be careful though, some of these missions can be missed. Here's what to do:
- Tali: Do NOT present evidence of her father's experiences.
- Samara: Get Morinth's attention and choose Samara at the end (or Morinth, but she's missing from Mass Effect 3).
- Zaeed: Don't let Vido get away, or convince Zaeed to drop it.
- Thane: Follow the politician.
Once the teammate loyalty missions are completed, two disputes await you on board -- one between Jack and Miranda, the other between Legion and Tali. You will need a high Paragon or Renegade score in order to resolve the dispute without losing the loyalty of one of the two.
In almost all cases, you need a high score in one of the two in order to complete Loyalty Missions perfectly, so you'd better not rush to complete them.
Remember to complete all your loyalty missions before going to complete the Harvester Wreckage mission, then you will only have time to complete the Legion loyalty mission before having to launch the final mission.
Start the final mission
When you are warned that part of the crew has been kidnapped, you have the choice between continuing to prepare, or immediately going through the Omera 4 relay.
You must go and rescue them immediately, otherwise there will be deaths.
Finally, you have to choose the right crew member for the right task during the different phases of the attack on the base.
Infiltration mission:
- Technical specialist: Tali, Kasumi or Legion
- Leader of the assault team: Garrus, Jacob or Miranda
The long walk:
- Escort the crew aboard the Normandy: Mordin ideally, if not then Tali, Jack or Kasumi
- Create a biotic field: Samara, Morinth or Jack
- Leader of the second assault team: Jacob, Garrus or Miranda
- Rearguard: Garrus, Zaeed or Grunt
The teammates you take to fight with you must also be loyal to survive.
Destiny of the Harvester base
You have the choice of destroying the base or irradiating its occupants in order to recover it, which will have some influence on the endings available in Mass Effect 3.
- Destroy Harvester Base (Paragon): You get the Harvester Heart, which makes the Destruction ending more accessible in ME3. The star behind the Illusive Man is blue at the end.
- Irradiate Base (Renegade): You get the Harvester's Brain, which makes the Control ending more accessible in ME3. The star behind the Illusive Man is red at the end. In the original game, this increased the point threshold required to unlock the enhanced endings of ME3 by 300 points. We do not know if this is still relevant.
