how does amir makeup for the rape of hassan in the ally?

In Amir's eyes, I don't think it is possible to make-up for standing by while Hassan was brutally raped in the alley. None-the-less, Amir later tracks down Hassan's son and brings him back to America where he will raise him.

Even with all the errors that Amir did, he did redeem himself in the end. By the time he was all grown up, he received a phone call from Rahim Kahn asking to come back to his homeland for a favor. And that favor ends up being an important decision: if he could try to find Hassan's son from an orphanage, and bring him back to America where he will live in a better environment. Because in reality, Afghanistan was not the right playground for any child to begin with.