There are several elements that make Poe's antagonist particularly unsettling and disturbing. The unreliable narrator of Poe's classic short story "The Tell-Tale Heart" is depicted as a neurotic, mentally unstable man, who claims that he is perfectly sane. However, in the first paragraph of the story, there are several red flags that suggest he is mentally deranged. The narrator's staccato, fragmented sentences, his insistence on being sane, and his ability to hear "all things in the heaven and in the earth" indicate that he is mentally deranged. The narrator proceeds to mention that he loves the old man and says that the old man's vulture eye is his sole motivation for murdering him. The incongruity between the narrator's feelings and actions once again reveals his mental instability. The sadistic thoughts and motivations of the narrator are significantly disturbing.
In addition to the narrator's deranged mind and confounding motivation, Poe’s antagonist proceeds to sneak into the old man's room when he is sound asleep for eight consecutive nights. Audiences find this method particularly unsettling because they can identify with the helpless, vulnerable old man. Simply the thought of a malevolent, deranged individual spying on you as you sleep is both disturbing and nerve-racking. The narrator then details how he suffocated and dismembered the old man's body before finally succumbing to his guilt and anxiety when the police arrive and begin questioning him. Overall, the narrator’s mental instability, his unsettling method of spying on the old man, and his horrific murder are what make Poe’s antagonist such a terrifying, unforgettable character.