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