Avengers Action Plan: if you want something shady done send a bloodthirsty X-Men. If anything goes wrong you can blame the mutants and disavow any sanctioning of their allegedly rogue actions.
If you're possessed by an alien force (or believed possessed by an alien force) and you kill a planet of broccoli-headed aliens, your friends will stick up for you.
If you're possessed by an alien force and you kill your former teacher, your friends will hate you.
If you're possessed by the Red Skull using the brain of Charles Xavier and you attack any mutant around, it's okay.
If you kill your own kids, both accidently and intentionally, you have the moral high ground in the above situations.
If you go back in time, creating a temporal paradox is a good, fun, safe idea.