What is the initial incident in "The Cask of Amontillado"?
In literature, the initial incident is that which generates action in the protagonist. In the short story "The Cask of Amontillado" by Edgar Allan Poe, the unreliable narrator named Montresor mentions that Fortunato, whom he considers his antagonist, has committed a "thousand injuries" against him. Then, Montresor names the initial, or inciting, incident: "...when he ventured upon insult, I vowed revenge." Thus, the initial/inciting incident is the unknown "insult" that Montresor claims to have borne at the hands of Fortunato.
This insult spurs Montresor to find Fortunato among the Carnival revelers and put his plan of revenge into action, a plan which is predicated upon Fortunato's "weak point": He takes excessive pride in his connoisseurship in wine. Montresor capitalizes upon this pride of Fortunato's by flattering him: "I was silly enough to pay full Amontillado price without consulting you in the matter." Then, Montresor acts as though he will consult another man because Fortunato is too busy. But Fortunato's pride will not allow anyone else to be conducted to the catacombs of the Montresors where the Amontillado is stored. He tells Montresor "Luchesi cannot tell Amontillado from sherry."
I agree with the previous post that the initial incident in the short story, "The Cask of Amontillado," is the offense that Fortunato commited against Montressor. Unfortunately, Montressor never reveals what Fortunato has done to him to cause the vengeful incidents that follow. We only know what the first lines of the story tell us.
The thousand injuries of Fortunato I had borne as I best could, but when he ventured upon insult I vowed revenge.
It appears that Montressor was unhappy with Fortunato's longtime treatment of him ("The thousand injuries"), but the last straw was the unnamed insult.
In my opinion, the initial incident in this story is not really even seen in the story. To me, the initial incident is whatever Fortunato did in the past to Montresor.
The initial incident is the thing that leads to the rising action in the story. To me, the rising action in this story is the interaction between Montresor and Fortunato as Montresor maneuvers Fortunato into going down into Montresor's wine cellars.
So the initial incident has to be whatever caused this to happen. In my opinion, that is the conflict between them that is only referred to in this story.