Dont get me wrong, there's nothing wrong with having a Villian that's a Villian just cause(as long as their interactions with the heroes are written well). But I want to believe theres more to him.

For starters, he mentioned to Ujiko that Shiggy was born with the twisted mind that would make him the next AFO. We saw how Shiggy was as a kid, before he killed his family, you wouldnt have expected kid Shiggy to turn into a murderous psychopath. There's also his possessive nature with his brother and the twisted version of love he shows him. Justifying his love for his brother because he's the only family that he has left. Part of me Hope's that this is fleshed out more. Maybe he was born with a twisted mind(as evident with how he only read the parts of the comic book where the Demon King won), but it was brought out or put on the forefront until something happened to his family presumably his parents. Maybe they were killed by quirk users rioting and that lead to AFO wanting to be in control or something like that.