A lot of people point to that line from the very end, but I'm always going to be hung up on what he says to Jung Heewon after the Peace Land arc. Something like 'Even if I become a villain, please become a hero.' That's the pivot, you know? The moment he accepts that his own path might be ugly, but he'll still push everyone else toward the light. It's not a heroic declaration, it's a desperate, messed-up bargain with the narrative itself.
Earlier quotes are all about survival, about being the 'reader' who knows the rules. The growth is in shifting from using that knowledge to save himself, to using it as a weapon to save others, even if it costs him everything. The later stuff about being 'just a reader' feels almost like a regression on the surface, but it's actually the final acceptance. He's not the protagonist, never wanted to be. He's the guy in the back making sure the story gets told, no matter what. That final, quiet ownership of his role gets me every time.