The main plot in "The Cask of Amontillado" concerns two wealthy individuals, Fortunato and Montresor; Fortunato appears to have done some great misdeed to Montresor. They are both in high standing, and so both could be considered "spoiled." However, in this context Fortunato appears to hold himself in high regard over others, and so has "spoiled" himself in regards to status and prestige.
He had a weak point -- this Fortunato -- although in other regards he was a man to be respected and even feared. He prided himself on his connoisseur-ship in wine. Few Italians have the true virtuoso spirit.
"Luchesi cannot tell Amontillado from Sherry."
(Poe, "The Cask of Amontillado," eNotes eText)
Montresor, already planning revenge, uses this aspect of Fortunato's personality against him; he is unable to resist the chance to show off his wine-tasting skills, and so follows Montresor into the cellar. His "spoiled" nature leads him directly into the trap. The revenge sought by Montresor was based on Fortunato's prior actions, but Fortunato's ego made the plan far easier.