????????? depends on how villainous you want to be. rather than list a catalogue of horrors, I will merely direct your attention to the three thousand years of recorded human history of conflict, genocide, and infamy.
She goes by Checker Monarch actually. I wrote that story. As for evil...She has an entry on the Complete Monster page on TV Tropes and was modeled off real life Sociopaths, that should be enough to tell you what she's like.
If you want to use her, feel free, I honestly don't mind people using my characters.
Still, I think your character is going to be awesome.
Good point. Though Checker's motivation was jealousy of her sister, but that was really just an excuse. She was really just wanted complete control over somepony's life and her sister was there. Checker was a master manipulator too.