The Butcher requires you to get 3 kills on enemy gods with Bakasura's Butcher Blades (his 3) in one game.
Butcher Blades is a move that increases Bakasura's damage for a small period of time. It is one of the better ways to get kills with Bakasura anyways so it shouldn't be that difficult. Building him crit and damage should make it pretty easy to get kills.