Complete the indicated task to unlock the corresponding Mutator.

Mutator	How to unlock
Big Explosions	Earn the Hail Mary ribbon 100 times.
Big Head	Earn the Gold Horder medal in Horde mode.
Comet	Earn the Gold Shock Trooper medal in Versus mode.
Enemy Regeneration	Earn the Silver Afficianado medal in Arcade mode.
Flower Blood	Earn the Silver King of Cog medal in Arcade mode.
Friendly Fire	Complete Co-op Campaign mode with four players.
Infinite Ammo	Earn the Combat Engineer ribbon 100 times in Horde mode.
Instagib Melee	Play as a Wretch and score 200 kills in Beast mode.
Laugh Track	Earn the Bronze Tour Of Duty, For The Horde, I'm A Beast, and Warmonger medals.
Must Active Reload	Earn the Silver Active Reloader medal.
Pinata	Earn the Gold Investor medal in Beast mode.
Super Reload	Earn the Bronze Master at Arms medal in Versus mode.
Vampire	Earn the Executioner ribbon 100 times in Versus mode.