Final answer:
In John Steinbeck's 'Of Mice and Men', Lennie, provoked by Curley's aggression, breaks Curley's hand during their altercation.
Step-by-step explanation:
The result of the run-in between Lennie and Curley in John Steinbeck's novel Of Mice and Men is that Lennie breaks Curley's hand. This conflict escalates when Curley, who is known for being aggressive and pugnacious, confronts and starts beating Lennie, who initially does not fight back due to fear and confusion. However, prompted by George, Lennie grabs Curley's hand, crushing it, and consequently needing medical attention. This event underscores the themes of power, violence, and camaraderie within the novel.