The usually don’t though. Garrosh was the bad guy, ordered people under him to do bad things, then the rest of the leaders took him out.
Sylvanas ordered people under her to do bad things, then I suspect in the end it will have all been for some greater good.
It’s never that the Horde are evil, it’s that theres always a rogue element that gives them a story for their xpac. Like Putricide.
Alliance rarely if ever have a story for their xpac. I think “babysit Anduin” was the biggest Alliance story arc.