Go Ape Shiv Achievement
Go Ape Shiv20
Kill an enraged, berserk Brute by melee, any level, any difficulty
At the beginning of the level "Gravemind" you will begin in a room with two large brutes. Kill one and the other one will freak out and drop to all fours and charge you. Simply jump over it and melee it in the back to kill it. Obviously easier on lower difficulty. Use a plasma shot to take its shields down first if you're having trouble.