Here is the full list of all 23 Space Hulk: Deathwing achievements.
Complete Devotion branch
unlock all Heavy weapon support's capacities in multiplayer
Kill 10,000 enemies
unlock all Tactical Terminator's capacities in multiplayer
unlock all Librarian's capacities in multiplayer
unlock all Apothecary's capacities in multiplayer
Complete Psy branch
Find all the relics
Learn Vortex of Doom
Learn Inferno
Complete Commandement branch
unlock all Assault Terminator's capacities in multiplayer
Kill a Broodlord
Kill a Genestealer's assault strain
Kill an hybrid psyker
Kill a Genestealer's warrior 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
Make 1111 assists