Here is the full list of all 66 Warhammer 40,000: Deathwatch - there are Enhanced Edition achievements.
Raise a Space Marine's Accuracy to 100%
Raise a Space Marine's HP to 400
Level a Space Marine to Level 50
Raise a Space Marine's Crit to 50%
Lose 10,000 XP from a single Space Marine
Level a Space Marine to Level 25
Collect all Grav Guns
Collect a Tier 4 Wargear
Open a pack containing only Tier 2+ items
Collect a Tier 4 Space Marine
Survive a shot from an Impaler Cannon
Level a Space Marine to Level 10
Unlock all of a Space Marine's abilities and traits
Complete Act 1
Complete Act 2
Complete Act 3
Complete Act 4
Complete Act 5
Complete Act 6
Complete Act 7
Complete Act 8
Complete the game on Normal difficulty
Complete the game on Veteran difficulty
Complete the game on Heroic difficulty
Equip a piece of Wargear in each of a Space Marine's Wargear slots
Enter a mission with a squad of Space Marines who have all of their abilities unlocked, and Wargear in every Wargear slot
Enter a mission with a squad Tier 4 Space Marines, using Tier 4 Weapons
Complete a mission on Veteran or Heroic difficulty, using only Tier 1 Space Marines with no additional Wargear
Complete a mission with a squad of Apothecaries
Complete a mission with a squad of Devastators using Weapons which cost 3AP to fire
Complete a mission with a squad of Space Wolves
Complete a mission with a squad of Ultramarines
Complete a mission with a squad of Blood Angels
Kill a Carnifex without it spending any AP
Kill one of each large Tyranid
Kill 40,000 Tyranids
Miss an overcharged plasma shot, only to be killed by the intended target on the next turn
Kill a friendly Space Marine
Heal a Space Marine when they were below 10 health
Avoid being killed when attacked, when a single hit would kill you
Complete a mission with a single survivor
Overcharge three times in a single turn with the same weapon
Kill an enemy in a single shot with an 8AP Overcharge
Complete a mission without attacking
Complete a mission on Heroic difficulty without a Space Marine being killed
Complete a mission on Veteran or Heroic difficulty without a Space Marine taking damage
Complete 'Longest Day' without triggering any mines
Collect all Bolt Weapons
Collect all Plasma Weapons
Collect all Flame Weapons
Collect all Melta Weapons
Collect all Melee Weapons
Collect all Missile Launchers
Collect all Lascannons
Collect all Grenades
Collect all Purity Seals
Collect all Shields
Collect all Miscellaneous Wargear
Collect all Space Wolves' Space Marines and Wargear
Collect all Blood Angels' Space Marines and Wargear
Collect all Ultramarines' Space Marines and Wargear
Collect all Weapons
Collect all non-Weapon Wargear
Collect all Space Marines
Collect everything in the Codex
Earn all achievements