Amir's Atonement

Atonement is defined as "compensation for a wrong" by the Merriam-Webster online dictionary. I believe that atonement for past mistakes is possible up to a point. Some sins never go away. These thoughts are just based on my personal moral code- doing something nice for someone you were rude to with might atone that particular "sin", but I don't think mass murderers can simply make their deeds disappear. Some things are forever. I think specifically in the Kite Runner, the guilt that Amir has been living with is much worse than any trials and tribulations he may have to go through to atone for his sin.
Amir seeks atonement for one particular sin. He watched his best friend, Hassan, get raped and does nothing about it. I would describe this a sin of weakness and disloyalty. In my opinion, he'd have to do something from the heart to help Hassan recover from this terrible loss of dignity. However, I think the event was more of a tragedy than bad conduct on Amir's part. He did not act in a terribly evil manner- it was how most people would react. That doesn't make it okay, but one cannot be too quick to judge him. Atonement is still necessary, though. This is just my opinion.