For this achievement you want Chapter 2, Level 10 called Full Moon Horde.
Work your way around the ice, without setting of the bomb that is in the middle of the Balverines. Once at the back there is a sword powerup that you can use to take out 6 or more Balverines to unlock the achievement.
EDIT: as suggested by x509cert you could get the puck close to the power up then use full power through the Balverines to hit the barrels and rebound into more Balverines