Steinbeck present Curley as a bully in chapter 2 in Of Mice and Men.
At that moment a young man came into the bunk house; a thin young man with a brown face, with brown eyes and a head of tightly curled hair. He wore a work glove on his left hand, and, like the boss, he wore high-heeled boots. “Seen my old man?” he asked.
The swamper said, “He was here jus’ a minute ago, Curley. Went over to the cook house, I think.”
“I’ll try to catch him,” said Curley. His eyes passed over the new men and he stopped. He glanced coldly at George and then at Lennie. His arms gradually bent at the elbows and his hands closed into fists. He stiffened and went into a slight crouch. His glance was at once calculating and pugnacious. Lennie squirmed under the look and shifted his feet nervously. Curley stepped gingerly close to him. “You the new guys the old man was waitin’ for?”
Curley stared levelly at [Lennie]. “Well, nex’ time you answer when you’re spoke to.” He turned toward the door and walked out, and his elbows were still bent out a little. (Chapter 2)
Curley is presented as hardworking ranch man, “Seen my old man?” who is easily antagonized in confrontationalism. Curley, the boss's son, watches both George and Lennie "coldly," starting with George and then moving to Lennie. Upon seeing Lennie's size, Curley's "arms gradually bent at the elbows and his hands closed into fists." He becomes "calculating and pugnacious." Even the language describing his hair features tension: "tightly curled hair." As Curley moves "gingerly" closer [carefully closer, as though approaching danger] to speak with Lennie and George, Curley assumes a confrontational position as he questions both men and demands that they speak when spoke to and remain silent when not spoken to.
Steinbeck further presents Curley as an antagonist. From the way he "lashed his body around" as he speaks to George to the leveled stare he gives Lennie, Curley is presented as an antagonistic bully. Steinbeck wishes to emphasize the difference between Curley and George and Lennie, with Curley as the enfranchised owner's son and George and Lennie the disenfranchised itinerant work hands. This presentation foreshadows the eventual conflict that will define the novella.