A predator is an animal that preys on other animals weaker than itself. The character in Of Mice and Men who best fits this description is Curley. Curley is the son of the boss of the ranch, and he exploits and abuses this position of power to prey upon the men who work on the ranch. These working men are dependent upon Curley's father for their jobs, and they are thus in a weak position relative to Curley. Through the character of Curley, Steinbeck shows that the predatory nature of humans is directly linked to the exercise of power.
About halfway through the novella, Curley decides to attack Lennie. Curley knows that Lennie is helpless and unlikely to fight back, and so he attacks Lennie with a cruel ferocity. He "slashe[s]" and "smashe[s]" at Lennie. Lennie backs away, "too frightened to defend himself," and Curley, as if hitting a punchbag, continues "slugging him in the face." Curley feels able to act in this vicious, predatory way because he feels that his position as the boss's son makes him untouchable. He knows that the men cannot fight back because if they do, they are likely to lose their jobs, and jobs were particularly hard to come by of course during the Great Depression of the 1930s. Curley feels able to give free reign to his predatory nature because he has so much power over these men.
At the end of the novella, Curley discovers the dead body of his wife. It is obvious that Lennie is responsible for his wife's death. Curley shows no signs whatsoever of grief for his dead wife, but he is instead filled with a predatory thirst for blood. He exclaims, "I'm gonna shoot the guts outa that big bastard myself...I'm gonna get 'im." The palpable sense of excitement in Curley's voice and the conspicuous absence of grief suggest that Curley's desire to satiate his predatory nature far outweighs any love that he ever had for his wife. He is driven by this predatory thirst for revenge. The suggestion here is that Curley's predatory nature is so strong because it has been fed for so long by his position of power on the ranch.