Maxperson
Morkus from Orkus
The Spellthief in in 3e that could steal spells along with the slot to cast that spell. I can't remember specifically, but I'm pretty sure that there were other ways to lose slots.Though you have to follow-through. As someone upthread indirectly references, its actually a bit odd that there's not much I've seen over the years that can damage spellslots other than indirectly by lifedrain back in the day. You'd expect there to be at least a few.

