Most evil souls in Skyrim

So I'm going to enchant a collection of magic rings on my next playthrough using black souls and naming them after the souls in question. But being resigned to the Soul Cairn forever is a fate I reserve for the very most wicked, depraved individuals. I'm making my hitlist, and here are some I've thought of off the top of my head:

Arondil: necromancer who murders young women and sleeps with their reanimated corpses

Calixto: necromancer who murders young women and rips their bodies apart for raw materials

Sild: necromancer who tortures people and enslaves their ghosts upon death

Eola: cannibal who targets innocents and public servants

Linwe: thief who kills his marks purely out of spite

Grelod: old woman who runs an orphanage so she can beat and mock orphans

I'm considering adding Mercer and Ancano, but really, I'd prefer souls more deserving. Even Linwe and Grelod feel like padding the list. Any suggestions? And don't field suggestions like Nazeem. I'm not asking for shmucks, I'm asking for monsters.

Edit: Per your suggestions, I'm appending to the list Movarth, the vampire who set out to enthrall all of Morthal, and Malkoran, the necromancer (or is it lich?) who enslaved the souls of those killed in the civil war.

Edit: Malyn, the mage who gobbles up peoples' souls to maintain a half-baked brand of eternal life, is going on the list as well.