You must hit a total of 10 raskulls with the Thunder staff power-up. Power-ups can be found in presents, and are completely random. There are multiple versions of the Thunder staff to be attained in presents. There is a single Thunder staff power-up and a triple Thunder staff power-up. Both do the same things. After you’ve attained the Thunder staff power-up, which looks like a purple staff, use to hit 10 enemies. The direction of the hit does not matter, as long as you make contact. Hit ten enemies and the achievement will unlock.
NOTE: This achievement is cumulative and does not need to be completed in one match.