Complete the indicated task to unlock the achievement.

Achievement	How to unlock
Bloody Mess	Unknown.
Marksman	Unknown.
Master of Motion Sickness	Unknown.
Mind Over Matter	Unknown.
Robin Hood	Unknown.
Sniper	Unknown.
The Butcher	Unknown.
The Exterminator	Unknown.
The Hunter	Unknown.
The Man with No Name	Unknown.
The Ravager	Unknown.
Viscera Showers	Unknown.
Walking Dead	Unknown.