Honestly? The worst I can recall was an NPC/filler type recurring comic relief in a Pokemon roleplay chatroom, a parrot named Ludwig. He wasn't dislikeable, but he hung around fights waiting for characters to die so that he could lightheartedly harvest their organs. Ludwig often turned up with mafia ties and regularly attempted to sell illicit drugs, and died very often.

I think you can tell that I prefer the top two layers of the alignment system.