Here is the full list of all 50 Dreamkiller achievements.
Complete Story mode on the Nightmare difficulty.
Complete a Single Player game in Time Trial mode.
Complete Story mode on the Bad Dream difficulty.
Kill 25 Enemies while teleporting.
Kill 300 opponents in any Multiplayer game mode.
Kill 100 opponents in any Multiplayer game mode.
Kill 25 opponents in any Multiplayer game mode.
Conquer 50 brains in Conquest mode.
Return your team's flag at least 5 times in one CTF match.
Finish a Deathmatch game with the highest score (with at least 3 other players involved).
Kill 10 opponents in a row without dying in a Multiplayer game.
Enter Berserker Rage during a Multiplayer game.
Kill 3 or more opponents at the same time in a Multiplayer game.
Complete one level in Story mode while only using the Dream Cleaner.
Complete one level in Story mode while only using Shock Therapy.
Complete one level in Story mode while only using the Sunbeam.
Complete one level in Story mode while only using the Minigun.
Kill 10 or more enemies at the same time with any weapon.
Complete one level in Story mode while only using the Hailstorm.
Complete one level without receiving any Health pickups.
Complete one level in Story mode while only using the Dragon's Grasp.
Complete every level on any difficulty without dying.
Complete a Single Player game in Single Weapon mode.
Complete every level on any difficulty without dying in the Subconscious.
Defeat a Doorkeeper without taking any damage.
Complete a level on any difficulty without dying.
Defeat a Dreamkiller without taking any damage.
Complete Chapter 4 on any difficulty.
Enter Berserker Rage at least once in each level of the game in Story mode.
Complete Story mode on the Insanity difficulty.
Achieve the Gold weapon upgrade rank on the Insanity difficulty.
Find and enter in all of the Secret areas in any one level of the game.
Complete Chapter 3 on any difficulty.
Use every weapon at least once in any level of the game in Story mode.
Complete Chapter 2 on any difficulty.
Kill 400 Enemies while using the Dream Cleaner.
Kill 100 Enemies while using the Dream Cleaner.
Kill 400 Enemies while using the Sunbeam.
Kill 100 Enemies while using the Sunbeam.
Kill 400 Enemies while using the Dragon's Grasp.
Kill 400 Enemies while using Shock Therapy.
Kill 100 Enemies while using Shock Therapy.
Kill 100 Enemies while using the Dragon's Grasp.
Complete Chapter 1 on any difficulty.
Die 5 times while in the Subconscious.
Die 10 times to self-inflicted explosives fire in any Single Player mode.
Kill 400 Enemies while using the Hailstorm.
Kill 100 Enemies while using the Hailstorm.
Kill 400 Enemies while using the Minigun.
Kill 100 Enemies while using the Minigun.