Double DeadG 15

To unlock this achievement you need to perform a double kill with a powerhouse special attack. You will need to level a powerhouse character to level 6. Once powerhouse is leveled to 6 you will have a defense skill available to you on the character tab. There will be two skills available called Pro Wrestling (This is a fun one) and Double Kill (You want this one for the achievement). Press X to chose the skill and hold X to make it permanent. The special move is executed by pressing LB + B when two zombies are in very close proximity to each other. If correctly executed you will grab both of their heads and smash them together for the double kill unlocking the achievement.