Who was the unlucky fellow in Cask of written by Edgar Allan Poe?

You're likely thinking of Montresor, the narrator and protagonist of Edgar Allan Poe's short story "The Cask of Amontillado."

While Montresor isn't necessarily "unlucky" in the traditional sense, he is the one who orchestrates the elaborate and gruesome revenge plot against Fortunato, the "unlucky fellow" who becomes trapped and entombed in the catacombs.

It's important to note that the story is told from Montresor's perspective, and he presents himself as justified in his actions. However, the reader can see the darkness and cruelty in his methods, making him a morally ambiguous character.