What is Montresor’s attitude toward revenge?

Montresor is very serious about the subject of revenge and views it as a moral obligation to right the wrongs suffered by one's enemy. Montresor's ideology concerning revenge corresponds to the motto written on his family's coat of arms, which reads, "Nemo me impune lacessit," or, "No one provokes me with impunity." Montresor also has a precise definition of revenge, which he describes in the first paragraph of the short story. Montresor mentions that, when exacting revenge, it is imperative that one "must not only punish but punish with impunity." He is essentially saying that it is necessary not only to punish one's enemy but also to do so without being caught or suffering the consequences of exacting revenge. Montresor goes on to say that an avenger will not feel satisfied unless the victim knows who is responsible for their punishment. After describing the ideal conditions involved in avenging one’s enemy, Montresor elaborates on how he committed the perfect crime by getting revenge on Fortunato. Montresor's calculating scheme and horrific crime emphasize the seriousness of his attitude toward revenge. Montresor's actions correspond to his definition perfectly, and Fortunato's fate is disturbing and shocking.

"The Cask of Amontillado" is all about Montresor's revenge: the terrible revenge he wreaks upon the hapless, misnamed Fortunato. We're never told exactly what Fortunato has done to Montresor that warranted being walled up alive inside the catacombs. But whatever it was, this unspecified insult has driven Montresor into a frenzy that can only be satisfied by some serious payback—the most terrible revenge you could possibly imagine.
In his warped imagination, Montresor feels that revenge is not just necessary, it is the right thing to do. Revenge is like a moral imperative for Montresor, something he simply has to do if he is to redress the "thousand injuries" that Fortunato has heaped upon him over the years. But if Monstresor's going to gain revenge, he needs to do it properly. That means making sure that he gets away with his crime. His elaborate revenge plot has clearly been carefully planned and worked out to the last detail. This is to ensure no one will ever suspect Montresor of having carried out this wicked, dastardly deed.