I lean more towards Anti heroes that don't take shit and will actually kill anyone for their own sake.
They don't go around saving people from dangers, but actually try to find benefits even in that situation.
I liked Fang yuan as a character in a novel, though I won't like him in real life as a person.
I like characters who are ruthless to people who deserve it, but wont kill the entire clan or family for simply being associated.
I like characters who accept the consequences of their actions without regret, simply upholding their ideals.
So, people who are REASONABLE. They can be assholes, too, but in a fun sense like you'd wanna drink a beer with them and hear their stories. Not in a way that you think, "i shouldn't mess around with this person"
As long as you respect their parameters, they can be friends. Otherwise? Well you may be fucked.
MC's who go, "if i leave the family alive, they may be thorns in my side later down the line....best kill them all just to be safe" i consider fucking pussies.
They are ruthless, but in the most cowardly way. Punish those who fuck with you. Don't drag innocents into it. So what if they hate you? If they later act against you? Accept the consequence of your choices, yeah?. Take some fucking responsibility for your actions. Act against them when they try to target you and those you love...not before.
So as i said. Ruthless, but reasonable.