How do I write an essay on moral responsibilities in The Kite Runner?

The importance of taking responsibility is the dominant theme of The Kite Runner, so an effective essay will depend on narrowing down an array of possibilities which show that centrality. One major consideration that the author raises is the relationship between maturity and self-knowledge in owning up to one's actions and their consequences.
Amir is the main character through whom Hosseini shows these processes developing. The key event is his turning his back on Hassan, which is related to seeking his father's approval. It takes years and many intervening events before Amir is ready to accept what he did, understand why he did it, and even more importantly, why it was wrong. The impetus for acquiring these insights, the author makes clear, is his genuine desire to help someone else—the young Sohrab—to not assuage his own guilt.
While an effective essay can certainly be written about Amir's story alone, a stronger analysis could incorporate another character. That might be someone who similarly changes, such as Baba. It might also be a contrasting character, such as Assef, who fails to demonstrate accountability.