The Ones That Last
Uncommon23.8%Beat the odds and walked into the sunset.
Awarded for the best possible ending where all faction leaders and all companions survive. This is mutually exclusive vs the other ending-specific achievements such as 
As with all of them, save before the point-of-no-return at Chapter 11. For this ending all companions must be upgraded to be "Heroes of the Vanguard", and you must have completed all regional quests to to get 3 stars with all the factions.
In the final missions, make sure to assign companions sensibly to roles that match their strengths so that they don't end up dying in those missions. Keep lots of saves so you can re-do if things go wrong.
You'll need to choose somebody to take down the wards - whoever you choose will appear as dead for a while but (provided they are a Hero of the Vanguard) they can be rescued later before the end and are not, in fact, dead.