I fixed him by making him a Mary Sumo.
He became more like the man I really am. Deeply insecure. Easily intimidated. Tormented by his past mistakes.
Now I had a character with flesh on his bones. He had much to learn, and I, in my megalomaniac role as author, set about teaching them to him in the usual way — through pain.
Because that's how it works in real life.
If we can call on the power of Mary Sumo (I believe), it doesn't matter how outlandish our fantasy worlds are, or how much willing suspension of disbelief we demand. Because I have no problem believing in unicorns, or singing swords, or mountains that fly. They don't offend my sense of reality. Only plastic, false, self-aggrandizing characters do that.