In Roald Dahl's story, "Man from the South," one man, Carlos, bets the narrator that he, the narrator, cannot successfully make his lighter light ten times in a row. If the narrator succeeds, Carlos says that he will give him his Cadillac. If he loses, however, then the narrator must allow Carlos to chop off one of his fingers. The men agree to the bet and go to Carlos's hotel room. In the hotel room, Carlos fastens the narrator's hand to a table and then asks a maid to fetch him a chopping knife. The narrator then begins lighting his lighter. Carlos is portrayed as something of a sadist. He seems to enjoy the prospect of being able to chop off one of the narrator's fingers. He stands to gain nothing other than the finger and the permission to chop it off. His evil is sadistic and entirely self-serving.
In "The Tell-Tale Heart" the narrator is similarly sadistic. One night, he sneaks into the room of an innocent old man and murders him in his sleep. He has no good reason for committing the murder, professing that he did it because he he took a violent disliking to one of the old man's eyes. This, however, is only an excuse. Like Carlos in "Man from the South," the narrator in this story commits his evil for his own sadistic gratification. His evil, like that of the older man in "Man from the South," is entirely self-serving and lacking a broader purpose.