Character development that surprises me is rare, which makes it notable. Most arc trajectories are telegraphed early — the reluctant hero who learns to accept their destiny, the villain whose backstory explains their choices, the mentor who dies to catalyze the protagonist. These aren't bad, they're reliable. What I'm looking for is the character who becomes someone I couldn't have predicted.

The arc that has stayed with me longest is Dalinar Kholin in the Stormlight Archive — specifically the flashback chapters in Oathbringer that reveal how he became the person he is. The reader has spent two long novels trusting this character and the flashbacks undermine that trust in a way that feels devastating rather than cheap. He doesn't stop being the character we trusted. We understand how he became capable of the things we didn't know about. That's a hard thing to write and Sanderson did it.

The other arc I think about is Ged's in Earthsea. The entire first trilogy is a character being undone and rebuilt. By the time we reach Tehanu and he is powerless, it feels like the inevitable conclusion of who he always was.