how is Amir and the antagonist in the novel are used by the author to develop the themrs of bestrayal and rethysion

It's difficult to isolate one antagonist in this novel but I think this might be what you are looking for,

These themes are seen throughout the novel and involve several of the characters on different levels. This might be a good question for the Discussion Board because of the various answers.

Amir, the protagonist, betrays Hassan- his best friend, Baba- his father, Rahim Khan- his father's associate, and Ali- Hassan's father. His betrayal to these characters is marked by one act that snowballs into several others, completely destroying any character and integrity Amir might have had. He watches Hassan get raped by Assef and says and does nothing to stop it. Then to make matters worse he is cruel toward Hassan. He beats him, he throw pomegranates at him, he is no longer willing to be his friend even though that is the only thing in the world Hassan wants and needs after his horrific experience. The final blow of betrayal was when he planted a watch and money in Hassan's matress to drive him away from his home. Ali and Hassan decide to leave after that. As life goes on everyone but Baba learns what happened to Hassan.

The redemption of Amir comes at the close of the novel when he is asked to rescue Hassan's son Sohrab from a war torn orphanage. Amir believes he can be redeemed if he can complete this task since Sohrab's parents were executed. Through the redemption process Amir faces his demons and triumphs over them finally giving him the peace he has searched his entire life.