What characteristics of the narrator in "The Cask of Amontillado"make him an effective villain?
Montresor is incredibly perceptive and has a keen understanding of others. He understands Fortunato's "weak point," his immense pride, especially in his connoisseurship of wine. Montresor knows just how to manipulate his enemy, offering Fortunato the opportunity to prove Montresor wrong in his purchase of the rare amontillado wine as well as to prevent the other local connoisseur, Luchesi, the chance to exercise his skills. He is well aware that Fortunato will not be able to pass up this opportunity to best him.
Montresor also understands his servants well enough to know that when he "told them that [he would] not return until the morning, and had given them explicit orders not to stir from the house," that they would absolutely disappear "as soon as [his] back was turned." Montresor is a keen observer of others, and he knows how to put their habits and tendencies to his advantage. This is likely why he thinks to bring his "mask of black silk, and . . . roquelaire": to hide his identity from any others who might observe him with Fortunato. In addition to his powers of perception and understanding, Montresor's attention to detail makes him quite a good villain.
Further, Montresor is adept at deceiving others; he is quite cunning. He says, "It must be understood that neither by word nor deed had I given Fortunato cause to doubt my good will. I continued, as was my wont to smile in his face, and he did not perceive that my smile now was at the thought of his immolation." His enemy doesn't suspect a thing, even when Montresor pulls a trowel, a brick-layer's tool, out from under his cloak! Montresor has done such a masterful job of pretending like everything is as usual that Fortunato even continues to insult him as they descend deeper and deeper into the catacombs.
Finally, Montresor holds a grudge. To begin the story, he says, "The thousand injuries of Fortunato I had borne as I best could; but when he ventured upon insult, I vowed revenge." Now, it seems unlikely that Fortunato had actually injured Montresor a thousand times, but to Montresor it feels as though he has. This grudge-holding, and his evident belief that revenge is a dish best served cold, make him a superb villain, as well.
Poe gives Montresor wonderfully villainous characteristics in "The Cask of Amontillado."
Montresor's murder of Fortunato is deviously premeditated. Montresor knows how he will lure him underground and how he will carry out the murder. He has everything in place to entomb the man before he even finds him, and he uses Fortunato's weakness for wine to guarantee that the man will agree to accompany him.
Other characteristics of Montresor's villainy include his pretense of concern over Fortunato's health. Repeatedly he asks after the other man's cough, and suggests they return above. The more he insists, however, the more Fortunato wants to continue on, which Montresor, no doubt, relies on.
Montresor also draws the other man's attention to the damp of the catacombs, knowing that soon he will entomb the sick man in the damp "cave" he has created for him.
Perhaps the most villainous characteristic of Montresor is his seeming madness. Although he never gives the reader a reason, and we can find nothing that suggests Fortunato deserves such treatment, Montresor is committed to taking the other man's life for what seems to be an "imagined" insult.
Montresor has many villainous characteristics which add to macabre mood Poe creates, yet again, in this short story.