Books about a person’s descent to corruption / “Power corrupts” theme

Looking for books with a character study on how one who was idealistic and principled and tracks their descent to corruption or evil as a consequences of gaining more and more power. I know Orwell's 1984 sort of touches on this theme. A Suzanne Collins' a Ballad of Songbirds and Snakes sort of does this too. Looking for more recs.

I'm open to any genre (litfic, historical fic, SFF), but preferably adult and not YA