What does it mean to be "evil"? When you look at a dictator, from the point of view of his oppressed people he would seem evil, but to his closest circles he won't appear evil, since he is doing things that benifit them and therefore he is not evil, that is how even the worse dictators of history came to power, he doesn't need to please everyone just the right people. Therfore to creat someone truly evil it had to be someone who only ever acts in his own intrest and never, NEVER act in others. But even then it there is still the possiblity of others liking what is done, but as long as the MC doesn't do it for them it should still work.
In my own story "Reincarnated as the monster of all monsters" that's exactly what I'm trying to protrate, the MC only acts in her own intrests never in others, she isn't alone in this, but it is stated on multipule ocasions that she doesn't see them as friends or the like, not even as people so to speak, she sees them as pets and nothing more.
There is, in my personal opinon, no way anything can truly be purely evil, there will always be some people out there defending others for their crimes even if 99% of people think otherwise, but we can come close. Torture and killing with no regard to life ever, it doesn't matter if its a child or a man, what race or what other people think, all that matters is that the MC wants to do these things for no other reason then his/her enjoyment.
"Some men just want to watch the world burn." Is a sentence one should have in mind if you are trying to write a character, that as many people as possible would consider truly evil.
