Everyone has their own opinions. Lets say this guy is the hardest/op zombie. State a reason like: "He's so op because he's hard to kill and turns my plants into sheep quick!" It could be any zombie. Even zombies from the Chinese version. And for plants this guy is OP because the plasma is strong, too bad there is a recharge. So state your opinions!
NOTE: Gargantuars are OP, so we are excluding them from this list.
NOTE 2: Instant plants can be counted, although they don't survive like other plants do.