Chapter 22 is the climatic confrontation of Amir and Assef. Amir has come to this place on a mission to get Sohrab, but it won't be that simple. He first must confront the physical and psychological cruelty of Assef. The psychological cruelty comes in many small and large ways:
1. He must enter the room alone, and he is surrounded by armed men who pat him down and are very intimidating.
2. He must sit and silence, observing a Talib man who is had blood from the morning execution still on his clothing and who speaks positively about the idea of public executions.
3. The Talib and the others pull off his fake beard, exposing him to be an American, which they ridicule.
4. The men in the room tell terrifying and gruesome stories about the Hazara massacre after the Taliban take over.
5. They taunt Amir and tell him he should be frightened right now.
6. They bring Sohrab in and his resemblance to his father is so striking that it almost takes Amir's breath away, but this only heightens Amir's need for this rescue to be successful. Failure is frightening.
7. Amir's long-lost enemy/bully, Assef, comes into the room and recognizes Amir from their childhood.
After Amir processes all of this psychological torture, he then must endure the physical torture of a the beating he receives from Assef. Assef uses brass knuckles to deliver the terrible blows as Amir swallows broken teeth, gets hurled against the wall, hasribs and facial bones broken by the brutality of Assef. The final straw for Assef is Amir's breaking into laughter over it all. This is not joyful laughter, but the laughter that comes when a person is actually feeling full out terror for his life. The cruel beating ends when Sohrab, so much his father's son, uses his slingshot to take out Assef's eye -- exactly like Hassan had threatened to do it when they were all youths.
The mix of psychological and physical cruelty in this chapter creates an immense amount of pathos in the reader, and we are as relieved as Amir when the chapter(scene) finally ends.