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