Here is the full list of all 54 Sentinel 4: Dark Star achievements.
Finish the campaign on Psycho difficulty
Kill 500000 enemies
Reach maximum level with any Commander
Use 1000 Stronghold abilities
Fully upgrade a turret in the armoury
Fire 1000 Sentinel orbital weapons
Complete campaign mission 26
Complete campaign mission 25
Complete campaign mission 24
Complete campaign mission 23
Reach Nexus rank 10
Complete level 10 (Titan) using only Laser Turrets
Complete level 2 (Fortification) using only path deployable weapons
Complete level 6 (Alliance) without losing any Xenite defenders
Complete campaign mission 22
Fire 100 Sentinel orbital weapons
Build 1000 turrets
Complete mission 5 of the second mini-campaign
Complete mission 4 of the second mini-campaign
Complete mission 3 of the second mini-campaign
Complete mission 2 of the second mini-campaign
Complete mission 1 of the second mini-campaign
Use 100 Stronghold abilities
Reach Nexus rank 5
Fire 10 Sentinel orbital weapons
Kill 50000 enemies
Complete campaign mission 21
Complete campaign mission 20
Complete campaign mission 19
Complete campaign mission 18
Complete campaign mission 17
Complete campaign mission 16
Complete campaign mission 15
Complete campaign mission 14
Complete campaign mission 13
Complete campaign mission 12
Complete campaign mission 11
Complete campaign mission 10
Complete campaign mission 9
Build 100 turrets
Complete campaign mission 8
Kill 5000 enemies
Complete campaign mission 7
Use 10 Stronghold abilities
Complete campaign mission 6
Complete campaign mission 5
Complete campaign mission 4
Complete campaign mission 3
Kill 500 enemies
Complete campaign mission 2
Build 10 turrets
Complete campaign mission 1
Kill 50 enemies
Buy every upgrade in the armoury