There are several other example of heroism in The Kite Runner. One comes when Amir decides to travel into Afghanistan to search for his half-brother, Sohrab. Just making the trip into the Taliban-held territory takes a great deal of courage; making contact with the Taliban in order to locate Sohrab ls another heroic step for Amir. Facing Assef and a probable death and then whisking the young boy away from danger is Amir's grandest gesture. Amir's driver, Farid, also risks his own life crossing the Pakistani border into Afghanistan and driving the getaway vehicle for Amir and Sohrab.
Wow! Great question, and if I may dare to make a suggestion to enotes I would ask them to move this into the discussion category as there are going to be a multitude of responses to this question. However, as I think back of my reading of this novel, to me there are two clear examples of heroism in this novel. For me, the first is Baba's defiance in standing up to the drunk Russian soldier when he and Amir are fleeing Afghanistan together and it is clear that this Russian solder will let them pass but only for sexual favours with one of the women. Baba reveals his customary defiance and courage and his ability to stand up for what he feels is right, even in the face of death, which is of course something that Amir is profoundly challenged and disturbed by, because every time Baba does this he is reminded of his inability to do so when Hassan needed him to be a hero.
The second, for me, is not based on a particular action, but rather a general way of living. I think it was heroic of Hassan to maintain his loyalty to Amir in spite of his knowledge of how Amir had abandoned him. I think it was immensely heroic for Hassan to persuade his father to move and leave Baba's household because of Hassan's understanding of Amir's guilt and shame that he did nothing. I think it was heroic of Hassan to maintain his loyalty to Baba and Amir even though it brought him death. I don't know if I would have been so heroic.