Mass Effect 3
68 Achievements
Savior
Free Omega from Cerberus Occupation.
How to unlock the Savior achievement in Mass Effect 3 - Definitive Guide
When you get to Afterlife and you're fighting off a wave of enemies whilst doing a set of 4 objectives, you'll unlock this achievement as you kill the last enemy and the 4 objectives.
This is the third and final achievement. The only missable achievement is 'Meticulous' and you should have gotten that before this achievement.
I couldn't say anymore without giving spoilers but you should need to know anything else for this achievement to pop.
This achievement is story-related and cannot be missed.
You will get it at the end of the last huge fight, when you're done securing the area, before you even go talk to Petrovsky. You will unlock your rewards at the same time.
Story related. If you want more info, continue reading. Otherwise, know that this will unlock through the natural progression of the story.
This will unlock after the final fight with Gen. Petrovsky. After Aria becomes trapped, you'll have to run around to the four corners of the room, switch off consoles, and then shoot four shield generators. You have to do all of that while being attacked by Cerberus troops. Shortly after clearing out the last troops, Petrovsky will surrender and the battle for Omega will be over.
This will unlock after the final fight with Gen. Petrovsky. After Aria becomes trapped, you'll have to run around to the four corners of the room, switch off consoles, and then shoot four shield generators. You have to do all of that while being attacked by Cerberus troops. Shortly after clearing out the last troops, Petrovsky will surrender and the battle for Omega will be over.