Fortunato appropriately wears the harlequin for the Carnival in Edgar Allan Poe's "The Cask of Amontillado." For, he is foolishly deluded, egotistical, and dull.
Fortunato is easily tricked by Montesor into coming to taste the Amontillado, priding himself that he is a connoisseur of wine. Montesor describes him, "Fortunato, like his countrymen, was a quack."
He refuses to turn back because of his cough, saying, "...the cough is a mere nothing; it will not kill me."
When Montesor suggests that Fortunato not expose himself to the cold by going into his vaults and that he will call upon Luchesi to taste the wine, Fortunato cannot bear the idea that another might be able to boast of having tasted a great Amontillado. So, he insists that Montesor take him:
Let us go, nevertheless. The cold is merely nothing. Amontillado!....And as for Luchesi, he cannot distinguish sherry from Amontillado.
When Montesor again mentions Luchesi's being able to go rather than Fortunato who has a cough, the latter refuses to allow anyone else to come,
"Enough...the cough is a mere nothing....
As they reach the deep recess, Montesor continues to bait Fortunato's ego, saying he will call upon Luchesi, Fortunato interrupts him, "He is an ignoramus."
When Montesor displays his coat of arms that has a motto which reads, "No one assails me with impunity," Fortunato does not understand its significance. Likewise, as Montesor creates a pun upon Fortunato's question about being a mason by swinging a trowel in the air, the dim-witted Fortunato does not comprehend.
With dramatic irony, Fortunato dully dismisses the idea of Luchesi's taking his place and steps forward into the deep recess. As Montesor throws the links of a chain around his waist and padlocks it, Fortunato is "too much astounded to resist," and then laughs, believing Montesor's actions a joke--at least, according to Montesor.
Fortunado has a weakness, his vanity, when it comes to his belief that he is a connoisseur of fine wines. Because he is drunk, he is oblivious to the warning signs around him; the warnings that he will not return from the catacombs. He seems to be unaware that comments he has made to the Montresor in the past have offended him greatly. So, I would say that he is not very sensitive when dealing with other people. His desire to sample and judge the wine before his competitor Luchesi shows arrogance. He has a trusting nature, perhaps brought on by the festivities and his overindulgence in drink. His trusting nature leads him deep underground beyond where wine would be kept.
All in all, I would describe him as a weak character in terms of dealing with others.