Loved the Embers of Illeniel series and I'm really digging where Phil Tucker's Immortal Great Souls series is going, and I'm looking for more. I like the progression elements of a weak/underpowered MC growing into a powerhouse over the course of the story, and I REALLY like said powerhouse using that strength to pay back everyone who deserves it. Looking for longer form stuff, and trolling through royal road and scribblehub just isn't scratching that itch.
If you don't mind sci-fi: Red Rising by Pierce Brown
And there's the classic The Count of Monte Cristo by Alexandre Dumas
The Count of Monte Cristo is what immediately came to my mind also. He is absolutely thorough in his revenge.