Who do George and Curley seek to control? How do they try to exert power/control over others? Is their reason for exerting power/control good or bad?
In Of Mice and Men, George and Curley show different extremes of control.
George exerts control in order to make life better for he and Lennie. He understands that he represents the thinking for both men. When he exerts control over Lennie, it is because he knows that Lennie trusts him. We recognize this when George tells Slim about when he was able to make Lennie jump into the Sacramento River simply because he told him to do so.
George knows that his control over Lennie is meant to keep him out of trouble and protect him. He also knows that their dream of "livin' off the fatta land" is only possible if he is able to control Lennie's actions. Without George, he and Lennie know that disaster is unavoidable. George's exertion of control is only meant for good. This can be seen in the end of the novella when George has to kill Lennie to prevent him from suffering at the hands of the lynch mob. George often laments about how happy he would be if he did not have to take care of Lennie, proving that his control of Lennie is for good purposes.
Curley's exertion of control is to demonstrate his own power. When he first encounters George and Lennie, his control is meant to substantiate his own power. His insistence on Lennie speaking when he is spoken to is meant to validate his stature. When he assaults Lennie, it is because he feels that he is losing credibility in the eyes of the other men in the bunkhouse. He uses control for his own ends. Even his continual searching for his wife is a way to exert control over her. Finally, he organizes the lynch mob against Lennie as a way to wrestle control of the situation. Curley rejects Slim's advice to stay behind to grieve over the loss of his wife because he wants to showcase his control of the situation. It is a way to demonstrate to everyone that he is the source of power. In all of these cases, Curley uses control for selfish and malevolent ends.