What are multiple signs of bullying that take place in the novel The Kite Runner?

How do you define bullying precisely? If you are after
examples of bullying during Amir's childhood, that is one thing, yet if you are looking
at violence between characters, that is a much wider issue that occurs throughout the
novel in a number of different contexts. I will assume you are referring to bullying
that occurs between children in the first section of the
novel.

Of course, the biggest example is Assef and how he
picks on both Hassan and Amir. This of course threatens to move into physical violence
but definitely is an example of psychological bullying. Consider this description of one
little run-in that Amir and Hassan had with Assef and his
gang:

Assef
slipped on the brass knuckles. Gave me an icy look. "You're part of the problem, Amir.
If idiots like you and your father didn't take these people in, we'd be rid of them by
now. They'd all just go rot in Hazarajat where they belong. You're a disgrace to
Afghanistan."

I looked in his crazy eyes and saw that he
meant it. He really meant to hurt me. Assef raised his fist and
came for me.

Of course, as
the narrator himself identifies (but in his older, maturer self who is looking back at
the action), Assef is a psychopath who delights in violence, but clearly Assef is
bullying Hassan and Amir because of Hassan's race. It is only the bravery of Hassan in
threatening to blind Assef with his sling that prevents Amir being beaten up by
Assef.

Therefore, if you are looking for examples of
bullying during the first stage of the novel, you need look no further than Assef and
his cronies who intimidate and bully Hassan and Amir because of his association with
Hassan because of Hassan's race.