Madam Medusa

Not all villains need a big push to serve the Friends' interests. Already an utterly vile individual, Medusa was approached by the Friends and pointed towards her goal (the Devil's eye), in the hopes that she would be able to defeat Bernard and Bianca for them, though she was unaware of the mice agents' existence at the time. While she was unsuccessful, the Friends simply abandoned Medusa to her fate living alone in the swamp to fend for herself when they were done with her. She most likely drowned.