Sometimes one gets tired of the good hero, the one who seeks out justice and tries to do the right thing. Whether it's trying to save everyone he knows, stopping a Young Master from bullying the poor guy, etc.
There are protagonist with a dark perspective on life, and I guess the closest one I've ever read is Omniscient Reader, not evil per se, but he only cares about a limited number of people.
People who were betrayed and are seeking revenge, people who sees the world as survival of the fittest and not afraid of crushing the weaker people.
There's the dual perspective, we can let off the Hero off the hook for killing a sect but assume that the Young Master is evil for doing the same thing.
How much evil can you tolerate in an MC? Will you bat an eye if he rapes someone? What if he murders innocent people to ensure his own survival? I mean in CEO novels, there are instances where the Male Lead rapes the Female Lead and he gets away with it, or the Female Lead thinks it's their way of showing love.
Needless to say, I'm curious on how f*cked up a protagonist can be :) Give me your best examples please!