Lemme rank em in my opinion
Well Mickey he didn't really have a real motive so not sure bout him
Jill definitely had the dumbest and most petty motive like imagining killing your own mother just for fame
Stu? peer pressure might sound somewhat reasonable but it ain't explored at all
Charlie is living proof people would go crazy for love
Mrs Loomis is a pretty simple concept of revenge so she's alright
Billy started the whole motive thing and actually was somewhat sympathetic
But the best motive I think should go to Roman Bridger hell I actually thought he was a tragic villain until I saw his pure evil page