Although we know little about the "thousand injuries" that Fortunato inflicted upon Montresor in "The Cask of Amontillado," we do know that he loves to drink. Montresor understands this, knowing that he will be able to lead Fortunato anywhere he wishes because of his weakness for alcohol. Montresor does admit that Fortunato commands respect and even fear, but this one vanity is a weakness that will cost him his life.
He prided himself on his connoisseur-ship in wine.
Montresor considered Fortunato a "quack" when it came to several of his other interests, but when it came to old wines, "he was sincere." Montresor knew that the temptation of a rare bottle of Amontillado was too much for Fortunato to resist.