Through his actions toward the end of the story, does Amir achieve retribution for the betrayal of Hassan during their childhood? In your mind, has he done enough to make up for that, or was the initial offense beyond retribution?

The sociopath Assef loosing his eye was a step in the right direction but I don't think physical retribution can really alleviate Amir's conscience. In the end only the rescue and adoption of Sohrab would begin to heal Amir's tortured soul. If there was one thing he could do for his brother and friend, Sohrab's welfare was the key.