Amir starts out saying to himself that it was okay to walk away from Hassan's rape because he was just a Hazara. Later, when he sent Hasan away by framing him for theft, he attempted to send his guilt with him however it was only multiplied. When he gets the phone call from Rahim Khan, Khan says "you still have the chance to be good" and by going back to Afghanistan, Amir takes blame for doing something wrong, he's started the path towards redemption. Skip to where Amir decided to help Sohrab after learning that Hassan was murdered by the Taliban. There's so many parrels here to Hassan. Sohrab is in the hands of Assef, Assef has been raping him, and Amir is faced with the same dilemmas as last time: with Hassan if he fought back he would have lost the kite and his father's approval and Hassan was just a Hazara. With Sohrab Amir knew he wasn't Hazara, they shared the same father but not everyone knew that and if he fought Assef, Amir would have lost his innocence. However, Amir is determined to find redemption and so he fights Assef and saves Sohrab. Later, much like in the phone call that started his journey of redemption, Amir ends it by finally telling someone what happened all those years ago in the ally, his wife.