It would be good to come up with as many different issues as you can to support each point in your essay. This shows the marker that you have a very good knowledge of the book and understanding of character. Therefore you might like to think about using the section where he threatens to blind Assef as an example of his bravery, comparing him to Amir at this point, but then find another example to use to talk about his unconditional love for Amir. When he refuses to relinquish the kite he has just ran for and gets raped instead would be an excellent episode to focus on. Or, what you could do would be to explore the following quote from Chapter 2:
Sometimes, up in those trees, I talked Hassan into firing walnuts with his slingshot at the neighbor's one-eyed German shepherd. Hassan never wanted to, but if I asked, really asked, he wouldn't deny me. Hassan never denied me anything.
The line "Hassan never denied me anything" clearly displays Hassan's love for Amir and the way that he would do anything Amir asked, even, as in this case, if it was something that he knew was wrong and would get him into trouble with his father. This in a sense foreshadows Hassan's death, as he dies standing up for Amir and his family. Refering to how this characteristic of Hassan is evident in his childhood would allow you to then go on and consider how in his adult life he continued to show such loyalty and unconditional love to Amir and his family, even though it cost him and his wife their lives.