What are two events that depict significant development of themes in The Kite Runner?

Since I think that one of the most important themes in the
novel is the idea of sacrifice and taking action, I think that the rape in Chapter 7 and
the confrontation in Chapter 22 are probably two of the most important events in the
novel.  When Assef and his buddies sodomize Hassan with Amir watching, it forms the crux
of the novel.  The need to "become good again" arises from this instant of cowardice. 
Amir's inability to demonstrate loyalty and support of his friend in the most painful
time of need is something that ends up haunting their friendship.  It is the pinnacle
moment that Amir goes back to time and time again.  It acquires even greater
significance when Amir has to fight Assef for Sohrab.  The same situation is played out,
only this time, Amir has the courage to set right what was wronged years ago in being
able to rescue Amir's son from Assef's cruelty.  It makes sense that while Amir is being
brutally beaten he starts to laugh.  This is the moment when Amir recognizes the
opportunity to "become good again" and also embraces both the sins of his own past as
well as the potential for redemption in the future.