What characteristics of Amir's have changed throughout the story?

Amir evolves from a scared boy torturing himself with the memory of his cowardness to a man determined to make amends. Amir will risk his life literally going into the den of the devil to help the son of a man he loved and betrayed. Amir was a much more confident and self-realized person by the end of the story. He had at least dealt with his sins.