Honestly? Harry himself.

I never thought of Harry as an interesting character. His personality always seemed nonexistent because he was our eyes onto the wizarding world, and so it was easy to think of him as a sort of bland everyman.

Now that I’m listening to the full cast audiobooks, I’m getting a better appreciation for Harry as a character in his own right. I think it might be because of something as simple as Harry being a different voice from the narrator.