i'd say tywin. he's driven to win no matter what and would easily commit atrocities if it ensured his victory. stannis has a supernatural edge but he doesn't use it during war, if i'm not mistaken. and his shadow baby making days are behind him.
fans don't forgive jorah? since when? i'd say there are some that do and some that don't. as for jaime, there are some fans that forgive him and some that don't. i really don't think there's a huge difference. that said, readers know jaime better than jorah so they may discuss him more frequently, giving the illusion that more have forgiven him. i think they've both done bad things and i think they both thought it would be easier to make amends for their actions than it really was. but i don't think one has it worse than the other.