I mean, that sounds very much like a paladin in unapologetic violation of one or more of their oaths.
I could see a Vengeance Paladin justifying through divine will or whatever
Yea, blatant murder and assault isn’t justifiable to most good deities or codes of ethics, even if the target pings as evil. “Oh this shopkeeper is evil? Guess he dies.”
At the least, it’s highly illegal most places, so even if there aren’t divine consequences there’d certainly be social ones.
Yeah, even when alignment is proof enough you still need trials, and a random person’s magic sword isn’t exactly reliable proof in itself.
Can it fail? Can it be tricked? Is it a magical effect, or a divine one?
What about people who have done horrible crimes but served their sentence?