Lennie killed George Because he was mad and vey upset .
Curley thinks Lennie's smiling is a sign of agreeing with the rest of the characters in the bunk house when they are all laughing at him. Curley also simply saw this as a chance to attack Lennie because being a small man, he had what the characters call "small man syndrome" and likes to pick on big guys, "Kinda mad at them 'cause they ain't a big guy."
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.
Lennie breaks Curley's left hand during their altercation on the ranch.
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 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 lennie's smiling at how small he is.Curley thinks that Lennie is smiling because of everyone else is bullying him after him and Slim had a disagreement. E.g after Candy got involved in the bullying by saying, "glove fulla vaseline" as an attack towards Curley.
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.
Candy thinks that Curley plans to shoot Lennie once he finds him, as revenge for Lennie accidentally killing Curley's wife. Candy knows that Curley is angry and vengeful, and he fears for Lennie's safety.
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.
George thinks he will probably be tangling with Curley because Curley is aggressive and constantly looking for a fight, especially with bigger guys like Lennie. George knows that Lennie's strength may provoke Curley, leading to a confrontation.
He took an arrow to the hand.
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.