Here is the full list of all 8 Echo Prime achievements.
Defeat the Wrecker Campaign Completed!
Reach wave 10 in an endless arena.
Level up 30 Echoes to Veterans.
Level up 60 Echoes to Veterans.
Reach wave 20 in an endless arena.
Reach wave 40 in an endless arena.
Locate Emptiness Campaign Completed!
Strange Alliances Campaign Completed!