Montoni's not the kind of guy you want to meet in a dark room. Emily's scared of him from the moment she meets him, though she's also kind of impressed:
Emily felt admiration, but not the admiration that leads to esteem; for it was mixed with a degree of fear she knew not exactly wherefore. (1.12.8)
Yeah, Em's got his character down pat. She's scared of him because she doesn't know what he's capable of doing.
The dude exudes power, but he's also got powerful friends. When the gang is traveling to Venice, Montoni stops to say hi to "the famous captain Utaldo, with whom, as well as with some of the other chiefs, he was personally acquainted" (2.2.9). Montoni's buddying up to some the fiercest warlords in the land? That must mean that he's got some serious clout.
If Montoni's got one thing going for him, it's that everyone assumes he's a criminal mastermind. Tony Soprano's got nothing on a guy who made Signora Laurentini "disappear," secretly killed his wife, and commandeered a group of outlaws in an Italian fortress.
Wait, is all that stuff true? Doesn't really matter, because someone's going to be whispering it to someone else. And hey, all those rumors add to his powerful image. Montoni's motto: it is better to be feared than loved. He wants you to be terrified, because if you're terrified of him, chances are that he'll be able to work his manipulative magic.
Montoni's the guy in charge at Udolpho, but he's always just one castle brawl away from being unseated. Although we know that he's not bad at dueling, he's got a bunch of minions at his beck and call who don't love being bossed around. And unluckily for Montoni, not everyone plays it fair and square by doing the sword fight thing. There are more devious ways to get rid of the boss—like, say, a cup of poison.
Bear with us, Shmoopers: maybe Montoni doesn't have a secret heart of gold under that Grinch-like demeanor. But he never actually does harm to Emily, either. Sure, he thwarts her marriage to Valancourt, takes her off to Italy, and makes threats to get her to sign away her properties. But he also duels Morano for her to make that creepy guy go away, and he sends her to Tuscany when the castle is under siege. For whatever reason, Montoni keeps Em out of harm's way while she's his houseguest.
Em pretty much thinks he's the worst, but a lot of that may be her own baggage. After all, he totally looks the part of the mustachioed villain of her favorite romance novels (we're sure the dude can rock a handlebar moustache like none other). But when she's worried about his thugs bothering her, Montoni says, "Have I not promised to protect you?" (3.8.47). We're not sure if he's sincere or not, but it's definitely up for debate.