Distinguish between Montresor at the time of the killing and Montresor at the present.
Since Montresor is telling the story after the crime, one can assume that he has not been caught for his crime. ( At least, not yet.) He attitude towards his crime is one of pride and confidence. His meticulous retelling of the killing is a sign that he relished every moment of the experience. He even relates how he felt before he committed the murder. He says," A thousand injuries of Fortuanato I had borne as best I could, but when he ventured upon insult, I vowed revenge." In other words, he often felt hurt by Fortuanato, perhaps because Fortunato was wealthy and Montresor's family had lost their wealth. Montresor is obviously extremely proud of his family's past. There must have been some feeling of inferiority. Even though Fortuanato had hurt him, the final straw is when Fortuanato insults him and probably insults his family name. Fortuanato implies this insult later in the story when he says, "Oh, I forgot. The Montresors were once a great and noble family." Montresor is also very cunning because he does not give Fortuanto "evidence of a threat". In other words, Montresor never lets Fortuanato know he should mistrust Montresor; he simply plans and carries out his murder and the unfortunate Fortunato doesn't even suspect his life is in danger until it's too late.