The problem is that all of the ones I find through google are humorous, not actually vicious.
Considering the circumstances, I've got one of my main characters going to the other one thinking she's done him a favor (by killing someone who she blamed for 'corrupting' him), and he replies with something like "get away from me, bitch."
Only I'm not sure whether they'd call people that or whether that's a more modern term.
'Harlot' was something I'd considered, but it's just not the right sort of insult for the relationship between the two of them. 'Swine' also doesn't seem to fit very well for the character.
Anyone know of anything? I'd try to get away with tone of voice, but he's the sort of character to throw in an insult, too.
And while we're at it, I know 'shit' was used at least in the Renaissance (oh Dante), but I don't know whether it reached the broad use today. Since one of the most important characters has a rather dirty mouth, what's an epithet he could mutter when in a lot of pain or in a difficult situation?