Here is the full list of all 23 Space Hulk: Deathwing achievements.
Finish a chapter without using a Psygate
Make 1111 assists
Complete Psy branch
Find all the relics
Complete Devotion branch
Kill 10,000 enemies
Learn Vortex of Doom
Complete Commandement branch
unlock all Assault Terminator's capacities in multiplayer
Kill a Broodlord
unlock all Librarian's capacities in multiplayer
unlock all Tactical Terminator's capacities in multiplayer
unlock all Heavy weapon support's capacities in multiplayer
unlock all Apothecary's capacities in multiplayer
Kill a Genestealer's assault strain
Hack a door
Kill 666 enemies
Learn Inferno
Destroy a door
Kill a Genestealer's stalker strain
Kill a Genestealer's warrior strain
Kill an hybrid psyker
Use the Psygate