The good guys are badguys now so which ones are the best at it?
Cyclops:
Went dark Phoenix and killed Xavier also has used harsh language and gang signs
Scarlet Witch:
Went crazy and commited genocide. Unlike Phoenix or Beast the genocide was commited against mutants not aliens so it's not ok.
Blackbolt:
Released a chemical weapon forcing many people to undergo terrigenesis and which now looks to be killing mutants.
Illuminati:
Destroyers of worlds