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