Curley fought with Lennie because he thought he was superior than everyone else on the ranch since he was the boss's son and since at that time, Lennie was laughing, Curley thought that Lennie was laughing at him. Obviously, as I said before, Curley thought he was better than everyone and he thought that he shouldn't be laughed at by such a low person so he punched Lennie because of his own stupidity and snobbishness.
Curley attacks Lennie out of rage and insecurity. He is a small man who feels threatened by Lennie's size and strength, and he targets Lennie in order to assert his dominance over him and prove his own toughness to the other ranch workers. Curley's aggressive behavior reflects his own feelings of inadequacy and a desire to prove himself.
Curley attacks Lennie out of anger and aggression, blaming him for the death of his wife. In retaliation, Lennie crushes Curley's hand, revealing his immense strength and inadvertently causing Curley significant harm.
Curley thinks that Lennie is making fun of him through his silence. Lennie is very large and Curley is short. Curley is defensive about his height and dislikes Lennie's silence.
Curley was in the bunk room beating up Lennie. Curley was looking for his wife and saw Lennie laughing. Curley thought Lennie was laughing at him when he really wasn't. Curley then started to beat up Lennie while George is screaming to Lennie to fight back. Lennie then grabs Curley's fist as he is about to punch him again, and Lennie crushes Curley's fist. The damage to Curley's fist was so bad he was taken to the hospital. Slim forces Curley to say his hand was crushed by a machine. There were hardly any bones left in Curley's hand, and Curley was crying.
At first Lennie doesn't fight back, but then George says get Curley to Lennie so Lennie grabs Curley's fist and breaks his hand and doesn't let go until George starts slapping him.
Curley wanted to fight George I think, so he picked on Lennie. He hit Lennie a couple times and then Lennie stopped a punch in mid-air and squeezed Curley fist and brokenit ending his boxing career. Then Lennie Lille Curleys wife and he runs away and George kills him. :)
Curley beat up Lennie in "Of Mice and Men" out of anger and jealousy. Curley was upset over his wife's flirtatious behavior towards the ranch workers, including Lennie. Being a small man, Curley also took out his frustrations on Lennie to assert his dominance and power over him.
Curley plans to shoot Lennie in the stomach, to cause a slow and painful death.
Lennie breaks Curley's left hand during their altercation on the ranch.
Curley's wife is implying that Lennie got the bruises on his face from fighting with Curley. She recognizes that Curley is quick to pick fights with the workers on the ranch.
One warning that George give Lennie is to stay away from Curley because he fears that if Curley tries to fight with Lennie, Lennie will hurt Curley, and they will lose their jobs. He also says to stay away from Curley's wife.
Curley dislikes Lennie because of his stature. Curley is a small man and therefore feels weak towards himself on account of that. On the other hand, Lennie has an enormous stature and powerful strength. Curley is probably jealous of his size and therefore dislikes him in an envious manner.