Plants vs. Zombies Garden Warfare

This achievement is really self-explanatory. All you gotta do for this is kill an enemy plant in a multiplayer match while you are a zombie.

In order to unlock this achievement, you will need to join any PvP game (I prefer playing the classic variant of the game mode you want to play, as it will make it harder for the other players that are used to using skins to kill you) as a zombie and kill any player. Most of the people on the server are noobs, so this should be fairly easy.