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