I rec'd desoto's "All Set Down" upthread, which isn't really about Giles being "evil" but rather ruthless because he has to be. (And it's a damn good fic.) And Molly_may rec'd another that I'm just starting - but I'm really surprised the theme hasn't been explored more often. I've seen post-Chosen/NFA fics that bash Giles for not helping save Fred when Angel called, I've also seen the occasional "Giles turned into a vampire fic", but that's it. It may have to do with what beer_good_foamy mentioned, that Giles became "too safe" on the series to make a villain but there's fics where every other character has gone bad, and the potential for Giles seems like it would be catnip for a fan writer.