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