Amir goes through quite a bit of change in the span of his life that the novel covers; however, he lives the majority of this life as a coward. Only towards the end of the novel does he truly redeem himself by finding the self-confidence he so adamantly believed he could never attain.
We see Amir in the beginning of the story as a scared boy who runs from conflict and cannot seem to live up to the expectations of his more powerful father - "Baba", his father, even states, "There is something missing in that boy." Further, Amir tries to avoid Assef and his friends and does not help his "friend" Hassan in his time of need when he is attacked - he even goes as far as framing Hassan after the event in a pathetic attempt to rid himself of his own guilt. Later in the story as Baba is dying, Amir fears being alone rather than being concerned for his father's welfare.
As the story progresses, however, Amir is forced to face his darkest fears and emerges as a stronger, more confident adult. One way this is developed is when he must return to his beloved homeland and sees what it has become. Also, he eventually encounters Assef as he searches for Sohrab: this fight with Assef somehow helps Amir overcome some of the guilt of his past choices.
Now that Amir has gained some confidence in himself, he is able to stand up to others, such as General Taheri. Amir also understands the value of friendship and unconditional love, becoming more of a selfless individual at the end of the novel.