Character Analysis
Inigo Montoya is the walking definition of a man with a mission. And that mission is to kill the dude who murdered his father. Inigo has spent his entire life learning to be a great swordsman, all in preparation for the day that he tracks down his father's killer and kills him. The only problem is that after training for decades, Inigo has realized that he can't track down his father's murderer. Which is strange, really, because the murderer had six fingers and there can't be too many guys milling around with that trait.
In any case, Inigo has grown into a private mercenary by the time we meet him. He has enough of a conscience to dislike much of the stuff he needs to do for money—like, say, murder Princess Buttercup. He is the first to tell his boss (the Sicilian) when he says:
"Well I don't like it all that much […] Frankly, I wish you had refused." (5.55)
He may dislike it, but he also doesn't refuse to do it. In his defense, though, Inigo is living in limbo until he finds his father's killer, since he can never forget the day the man with six fingers murdered his dad and left two scars down his (Inigo's) cheeks: "And Inigo's face began to bleed. Two rivers of blood poured from his forehead to his chin, one crossing each cheek" (5.375). He is pretty much constantly haunted by the memory of this experience. In other words, he may not demonstrate strict morals, but he's also had his world turned upside down.
Perhaps the best example of this—besides Inigo's repeatedly bringing his father's death up, that is—is the fact that by the time Inigo becomes a mercenary, he has also become a world-class drinker. He's a man with a habit for drowning his sorrows. After he loses his boss, the Sicilian, the bottle is the first place he turns:
He sat alone and confident and strong. His life was straight and fine. He had money enough for brandy, and if you had that, you had the world. (6.23)
After all, the only thing that has made the guy's life worth living is sword fighting and revenge, and now that he's been beaten at sword fighting and he can't find his father's killer, well, he just can't find much to live for. So he drinks. Luckily for him, though, he's got a good friend in Fezzik, who helps sober him up and tells him where to find the six-fingered man. And yes, Inigo does end up killing the guy and getting his revenge.