The 'Justice' speech he delivers on the bridge in Marineford is probably the purest distillation of his philosophy. He's talking to Crocodile, I think, and just lays it out: 'Pirates are evil? The Marines are righteous? These terms have always changed throughout the course of history!' He's not just a thug; he's a nihilist who sees the entire world as a power game where the winners get to write the moral code. Anyone who believes in absolute justice is, to him, a fool clinging to a fairy tale.
That ideology explains everything he does in Dressrosa. He created a literal puppet state where he controlled the narrative so completely that he was a beloved hero while committing atrocities. The quote about the throne, 'The Throne of the King... it exists above all,' ties back to this. He doesn't want wealth for its own sake; he wants the ultimate authority to define reality for everyone beneath him. His villainy isn't about chaos; it's about constructing a 'peaceful' world where he alone decides what is true and false, righteous and evil.
It's chilling because it's a very coherent, almost intellectual brand of evil. He sees the hypocrisy of the world and uses it as an excuse to abandon any morality himself, positioning his own desire for control as a kind of superior, clear-eyed realism.