What does the Swamper mean by the statement: "Curley's pretty handy?"

Candy means that Curley was good at boxing in his weight class.

In "Of Mice and Men," the statement "Curley's pretty handy" means that Curley is skilled at fighting. It reflects his aggressive personality and tendency to assert dominance over others, creating a sense of tension in the story. This remark foreshadows potential conflicts, particularly involving George and Lennie, as Curley often seeks to provoke those he perceives as weaker. https://wheelielife.io/

Old Candy used this word to warn George and Lennie that Curley was very aggressive, arrogant, and liked to pick fights with bigger people to compensate for his own short stature.