War and its consequences, such as human rights violations, are powerful forces that not only change people but also nations. In light of this, Baba and Amir, the two main characters, changed drastically.
First, Baba had to leave what was familiar and what he loved--namely, his home. Along with this geographical loss, he also lost standing and honor in society. Eventually he makes his way to California, but he is a worker at a gas station; he is a shadow of the person he was before. This changes him. However, I would say that the movie does a good job of showing Baba as a courageous man.
Second, when it comes to Amir, he changes as well (and more drastically). He cannot live with himself for what he did to Hassan. More precisely, he could not live with himself for what he allowed to happen to Hassan, rape. Therefore, Amir gains courage, and redeems himself, to rescue Hassan's son. In light of this, we can say that Amir is a new man and faces his demons to find redemption. From his perspective, we can also say that, as Amir has to deal with the Taliban, his desire for human rights and protection of children grows apace.