In Of Mice and Men, Curley is short, angry and cruel. These characteristics describe everything this character contributes to the novel.
Curley is short and has a bit of what is known as the Napolean complex. So he goes around angry trying to start fights. The second time the reader meets Curley, he attacks Lennie thinking that Lennie was laughing at him. He punches Lennie in the face, which causes the large man to bleed. Lennie did not fight back until George told him to, but when he does fight back, he crushes every bone in Lennie's hand. This is what Candy says about him after this incident:
Curley's like a lot of little guys. He hates big guys. He's alla time picking scraps with big guys. Kind of like he's mad at 'em because he ain't a big guy.
Curley's inadequacy that may stem from his height is also evident in how he treats his wife, who is known simply as Curley's wife. He supposedly keeps his hand in a Vaselined glove so it'd be soft when he touches her, but there's absolutely no evidence he ever touches her. He shows no connection with her other than constantly looking for her. In fact, the only time the reader hears about Curley being sexual in the novel is when he goes to Old Susie's, the town whorehouse.
Finally, it's important to note that there is really no evidence of mourning when Lennie kills Curley's wife. Instead, Curley just wants to go out and kill Lennie.
Lennie is a fat ass cow who is dumb as rocks and can't do anything without George.