A lot of players try to complete the Mass Effect 2 suicide mission thinking that having a loyal crew is enough to keep them all alive. Unfortunately it is not. Having a loyal crew is one of quite a few important parts needed to ensure you obtain the Mass Effect 2 crew survival achievement 'No One Left Behind'.
It is very important that every crew member is loyal to you. Having even one that is not could jeopardize their own, or several other crew members survival. You can gain the loyalty of a crew member by completing their loyalty mission. During your play through of Mass Effect 2 you should routinely speak to each crew member to see if any new conversation options have appeared.
Playing The Peacemaker
At different points in the game you will find yourself caught in the middle of other crew members' arguments. In order to retain their loyalty you will have to select either the Paragon or Renegade option in the conversation if you do not, or they are grayed out then you will find that the crew member you told off will stop speaking to you. In order to remedy this, you can try to talk to them after the fight and choose either the Paragon or Renegade option. If you are finding that both options are constantly grayed out, then you should consider trying to either max out the Renegade or Paragon bar or retraining your skills so a passive skill maxes them out for you.
Having all the ship upgrades is also very important for the Mass Effect 2 crew survival achievement. If you do not have all the upgrades you may find that one or more of your crew will die on the journey to and battle with the collector ship. The Normandy's guns, shields and armor need to be upgraded to ensure everyone survives. You can get these upgrades by speaking to your crew and asking them about ship upgrades. It is definitely worth getting all the upgrades that the crew suggest just to make sure they survive the suicide mission.
The following crew members will suggest these necessary upgrades:
Jacob – Heavy Ship Armor upgrade
Garrus – Thanix Cannon,
Tali – Multicore shielding
Samara – Extended Fuel Cells
There are also other upgrades available from the rest of the crew, but they are not all directly related to the ship surviving its trip through the Omega 4 Relay.
Going Straight Through The Omege 4 Relay
I cannot stress enough how important it is that you enter the Omega 4 Relay straight away. Completing side missions after you activate the IFF and your crew has been taken will ensure that they do not survive. If you do any side missions before entering the relay, when you do eventually find your kidnapped crew, some of which will be dead, they will ask you what took you so long, and they are being quiet literal here. If you enter the relay directly after the kidnapping you should find that your entire crew has survived and can be sent back to the Normandy.
Making The Right Decisions: The Ventilation System
When you have finally reached the Collector base you should find Shephard addressing the crew on the Normandy. You will now have to decide which crew member should go through the ventilation system. In theory it should not matter whether it is Tali, Legion or Kasumi as long as they are loyal to you, but for various reasons they might die during the mission therefore it is important to save your game a lot. Most players seem to have the most success with Tali in the ventilation system.
Miranda will then suggest you make her leader of the second team. Again, it should not matter whether you chose Miranda, Jacob or Garrus to lead the team once they are loyal to you.
Selecting A Biotic Specialist
After fighting your way through the Collectors, and helping your chosen character through the vents you will be faced with another potentially difficult decision. A biotic specialist is needed to create a barrier around you and your team from the seeker swarms. Miranda will again offer herself – do not choose her! Using Miranda for this part of the mission will almost certainly result in at least one character's death. Choose Jack, Samara or Morinth and, once they are loyal, you should all survive.
Finding Your Crew and Picking Your Final Team
When you find your kidnapped crew you should always choose to have them escorted back to the Normandy or they will die. You can have any loyal crew member escort them, I usually choose Mordin as he is not very reliable in battle and this is an easy way to ensure his survival.
For the final battle choose any characters that you feel may die if left to their own devices, for example – I think we all know that Grunt will most likely survive on his own easily while Miranda may struggle (this is a personal experience – she never lives if I leave her on her own at the end). In short keep anyone you feel is weak in your final team so you know they won’t die.
If too many characters die during the Collector mission it could eventually result in Shephard being killed so be careful out there.