Final answer:
Red Chief causes difficulty for Sam and Bill because of his mischievous and rambunctious behavior, which exhausts them and makes them regret kidnapping him in O. Henry's 'The Ransom of Red Chief'.
Step-by-step explanation:
Red Chief, the nickname given to the boy in O. Henry's short story 'The Ransom of Red Chief', causes a great deal of difficulty for Sam and Bill, the two kidnappers, because he turns out to be more than they can handle. The boy is mischievous, rambunctious, and completely undaunted by the experience of being kidnapped; instead of being scared, he views it as an adventure. His relentless energy, pranks, and aggressive playfulness exhaust the two men and make them regret their criminal endeavor. The irony in the story is that the kidnappers find themselves at the mercy of their captor, resulting not in the anticipated payday, but in desperation to return the boy and escape his torturous antics.