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