In which parts of the book " The Kite Runner" is shown that Amir feels guilty?Amir felt guilty when he betrayed Hassan who always stood up for him.

The book opens in the adulthood of Amir and he relates
then and there that he made a bad decision in his childhood and he has spent the rest of
life to that point trying to redeem himself.  Then the book slides into a flashback and
we learn what bad decisions he makes, namely his poor treatment of his friend Hassan,
and his not trying to stop Assef's attack of Hassan after the kite running contest.  He
reveals his guilt immediately after the attack when he talks about why he didin't react;
he reveals it in his subsequent horrible treatment of Hassan and his false accusations;
he reveals it in a comment here or there throughout the novel as he tells about leaving
Afganistan and his life in the United States.  He specically thinks about it when he
learns about the mistake his wife made in running off the man.  She can reveal her sins,
while Amir states that he just can't. 

His guilt hits him
hardest when he hears from Kahn and learns that he needs to return to Afganistan.  Once
there when he learns that Kahn knew the whole truth all this time and that Hassan is
actually his half brother, the guilt is almost overwhelming and he is driven to atone
for that past by doing everything in his power to save Sohrab from the Taliban men and
Assef.  He devotes himself to bringing Sohrab home and healing Sohrab's spirit in a way
he never did for Hassan. 

There are references to his guilt
in almost every episode of the novel -- it is so clearly a novel about guilt and
redemption, and it works well because we are never left too long without a reminder of
what Amir did and his feelings about those childhood actions.