Answer:
Amir is cruel to Hassan in two instances: he witnesses Hassan's sexual assault by Assef and does nothing, and he plants his belongings under Hassan's mattress and accuses him of stealing. These acts stem from Amir's jealousy and feelings of inadequacy. The relationship between Amir and Hassan mirrors that of Baba and Ali, characterized by inequality and loyalty/betrayal. Baba is secretly Hassan's father, adding to the sense of betrayal towards Ali. These relationships reflect the novel's larger themes of social inequality, loyalty, betrayal, and redemption.