Some examples being Rin from poppy war, Eren Yeager from Attack on titan. Where their hate and vengeance degrades their morality as the story progresses. While not vengeful Paul from Dune also fits as his morality degrades throughout the story. Also early thorfinn from Vinland Saga before the slave arc fits the bill. Some Movie examples would be Kill Bill, Old Boy, Memento, I saw the devil.
I have read Count of Monte Cristo. I also really liked best served cold, the standalone from the first law series. I appreciate all the recommendations
Eren is the best example I can give. He's just fuelled by pure rage and anger the entire way through and keeps moving forward irrespective of what happens and how far he needs to fall. Also I love Fantasy/Sci-fi so that's preferably but I don't mind ither genres at all
by No-Pomegranate6308