Biggest cheater is obviously Jones hands down. Eye pokes, knee kicks, steroids, he just needs to add a good groin kick to his repitoire and a few extra minutes on the stool between rounds nobody would ever surpass him.
If we're not going for the obvious Jones then the next biggest cheater imo is Yoel. I love the guy, but fuck is he a dirty fighter, almost pulls something every fight. Lmao
Dunno who the least cheating is, I guess Frankie Edgar gets my vote. Fought most of his career a weight class above his natural, beat the GOAT of that weight class always fought bigger guys. Doesn't exactly seem like a poster child for steroids either, just a hard working dude who loves to scrap. Not a weight cutter, not a steroid user, not an eye poker.