This brings up two very fascinating points of view of psychological torture for both Fortunato and the reader himself!
Fortunato is obviously being played by Montresor for some insult upon his family, which is never actually revealed.
Psychological torture begins the moment Fortunato (along with the reader) enter the catacombs in the supposed quest for amontillado. The setting of the deep, dank catacombs lends itself particularly well to some of our darkest fears of enclosed spaces, damp creepy passage ways, and overall suspense as we follow along with Fortunato, knowing that no good is going to come of this excursion. Tools of psychological torture within these walls become even more powerful as Montresor feeds off Fortunato's greed for fine wine, as each step brings the character and the reader to the awful ending. Devices such as the jingling of the bells, brought up repeatedly by the author, as well as the lingering cough suffered by Fortunato, not only heighten suspense, but notch up the torture factor immensely for both reader and character.
The reader has a sense of foreboding and foreshadowing that revenge is going to be Montresor's end game, but we really don't know exactly what punishment awaits. This is the perfect device that Poe uses in order to grasp the reader's sense of impending doom. What can be more psychologically tortuous than both knowing and not knowing something awful is going to happen to Fortunato AND the reader's sensitive capabilities to empathize with the main character's unknown fate. The whole grisly scenario of being buried alive plays upon one of the basest fears of humankind. The slow suffocation and building epiphany of Fortunato's awful end are psychological torture in themselves. Panic starts to set in, as each brick is placed securely for the burial.
The ultimate torture is Montresor finally abandoning Fortunato in his tomb of bricks, to whither and die a slow, lonely, and miserable death. Montresor wants Fortunato to bear witness to his own demise, as he has borne quite enough insult at the hands of Fortunato. The reader can merely cringe at the end of the story, as Fortunato surely realizes he will die inside the encased wall. The faint jingling of the bells intensifies this torture. Desperation creeps in and settles upon the victim, while the reader is left with the realization that this is indeed a terrible way to die.
I would say that the most effective form of psychological torture in "The Cask of Amontillado" is Montresor not killing Fortunato in the cellar and then burying him. Montresor led Fortunato down to the wine cellar, and then Montresor chained him to a recess in the wall.
A moment more and I had fettered him to the granite. In its surface were two iron staples, distant from each other about two feet, horizontally. From one of these depended a short chain, from the other a padlock. Throwing the links about his waist, it was but the work of a few seconds to secure it. He was too much astounded to resist.
It's clear from the text that Fortunato is too drunk to do anything about it. Montresor could have easy killed him with a knife of something (he was even wearing a sword) and then buried him in the wall. Instead, Montresor left him alive, which allowed Fortunato to sober up enough to realize what was happening and begin begging for his life.
A succession of loud and shrill screams, bursting suddenly from the throat of the chained form, seemed to thrust me violently back.
The realization that he was being buried alive must have been horrible psychological torture for Fortunato. But it wouldn't have ended there either. After Montresor finished the brick work and left, Fortunato would still be alive and would be so for a few more hours (or even days depending on air). It would be awful.