>>24527872 (OP)It isn't necessary. When your protagonist is a son of a bitch the audience will get to witness his thought process, his justifications, his mental gymnastics--or his simply disinterest in the subject of morality. Spelling out in bold letters that the guy is evil is usually redundant and lazy.
Modern people don't actually have morality anymore, they derive their sense of what is right and wrong from social signaling of acceptability/unacceptability than from any higher moral principles--and this means that generally they feel uncomfortable unless an authority (not an authority figure per-se, but rather affirmations of social consensus) reiterates very clearly that someone is a good or bad person.
This is the exact reason why you shouldn't do it. Forcing your reader to actually make a moral judgement on their own without someone holding their hand is one of the most revolutionary things you can do in the modern day. It doesn't have to be a complex gray morality either, you can make it black and white but then just not label it black and white and it will still make normgroids uncomfortable.