So Jayne joined a different group that gave him a better offer. He was fairly loyal once he joined and seemed to actually bond with them. In the episode where he was the hero of the town, he shows compassion. In addition, he didn't kill his former employer he just shot them in the leg. CN means some of the things you do could be considered evil, some good.
In any case as I said before I don't try to figure out alignment from the outside, I'm just saying that if I were in an RPG playing Jayne I think I would consider what he did in line with a CN alignment.
As far as CE, The Joker is
an extreme case, that's what I meant by "epitome".