The thousand injuries of Fortunato I had borne as I best could, but when he ventured upon insult I vowed revenge.

The opening sentence of the story provides the extent of our understanding of Fortunato’s trespass. Although the “thousand injuries” may sound more serious, this single insult is what upsets Montresor to the point where he desires revenge. We do not know what those injuries may have been, physical or verbal, but an insult can only hurt one’s pride. It’s frighteningly clear from this first sentence that pride is Montresor’s primary motivation, which makes his cruelty seem all the more dangerous and irrational.

Let us go, nevertheless. The cold is merely nothing. Amontillado! You have been imposed upon. And as for Luchesi, he cannot distinguish Sherry from Amontillado.

Fortunato makes this comment after Montresor once again urges him to turn back after a coughing fit. Here we see how thoroughly Montresor has played on Fortunato’s pride so that he refuses to take his own best interests into account. Even if Montresor did not have murderous intent, the vault appears to severely aggravate Fortunato’s cough, and it would be smart for him to turn back. Once again, pride proves a powerful motivator, although an unwise one to turn to.