Baron Harkonnen is the ur-example of this trope. Described as so humongously gluttonous that he requires anti-gravity generators in his clothing just to hold himself up. Mentioned as being "baby-fat", so get out a picture of a fat baby, and then imagine a full-grown man having that percentage of body fat! Eww.
In the somewhat contested prequel novels, the Baron's obesity is actually a consequence of a disease he contracted when he violently coupled with Mother Gaius Mohiam to conceive Jessica as per his agreement with the Bene Gesserit. Mohiam inflicted the disease on him as payback for his brutality during the act. When he learned that it was incurable and untreatable, the Baron decided to invoke this trope to let his enemies think that his obesity was a sign of indulgence and excessive wealth rather than a sign of weakness.
A few villains in Redwall: Clogg, Bowfleg, Agarnu and Bladd. Clogg is known to eat/drink whatever may be by his side when he wakes up.
In The Hobbit, the three trolls William, Bert, and Tom are Obsessed with Food, the first thing Tom wonders about Bilbo is how edible he is; William decides against it, because he's too small. They see the dwarves as much more appetizing. Once they are tricked into staying out until the sun rises, turning them to stone, inspection of their cave finds the remains of several victims.
The arachnid Shelob in The Two Towers (which is covered in the Film adaptation of The Return of the King). She wants nothing more than to consume everything she can, orc, man, elf, or hobbit.
Ungoliant, Shelob's mother from The Silmarillion, also wanted to consume everyone. In the world. Even Morgoth, the Big Bad of those days, was scared of her. And for a good reason — Ungoliant ate all the artificial gems Morgoth had stolen, after having drunk all the Light of the Trees. *burp*. She would have eaten the Silmarils and Morgoth if he had not summoned some Balrogs to drive her off. Eventually she went North and ate herself. Ungoliant's probably the closest the LOTR universe has to a genuine Eldritch Abomination, and the codifyingAnimalistic Abomination.
Sydney Greenstreet's portrayal of Wilkie Collins' classic character Count Fosco in the film of The Woman in White was in keeping with his portrayal in the book; more recent portrayals, sad to say, have not been.
Each of the villains in the Keys to the Kingdom series represents a deadly sin, with Drowned Wednesday representing gluttony. This trope is averted, however, when it turns out that she is no longer a villain.
In Eoin Colfer's The Supernaturalist, Mayor Ray Shine is suggested to be huge, and is most villainous.
In Michael Chrichton's Timeline, the protagonists are surprised to see that this trope is inverted. The "good" king is the one with Jabba Table Manners, stuffing huge gobs of meat into his mouth constantly, while the "evil" king has perfect manners.
The appropriately-named Casper Gutman from The Maltese Falcon. (Dashiell Hammett, in his earlier career at a detective agency, was involved in the Fatty Arbuckle case, and some thing his fondness for fat villains stems from that.)
In the Rainbow Magic series, while most of the goblins aren't fat, they're very greedy when it comes to food. One of the conflicts in the Sugar and Spice series came from them eating Jack Frost's Candy Castle.
Hideously exaggerated in David Eddings' The Elenium with Otha, emperor of Zemoch and technically The Dragon to Big Bad evil god Azash (other more competent men are more effective Dragons). Nineteen hundred years of engaging in every imaginable form of excess, vice, and debauchery, combined with never leaving his palace complex, have turned him into a kind of slug-like monstrosity probably not unlike Jabba the Hutt.
Crabbe and Goyle from Harry Potter do like food quite a lot. Which makes it easier for Harry and Ron to get some hairs in Chamber Of Secrets: levitating cakes laced with a sleeping potion in front of them. And just like that, they fall for the trap.
Charlie and the Chocolate Factory: Augustus Gloop, an child who simply cannot resist chocolate, and eats pounds of it at a time. He ends up sticking his unwashed hands into a chocolate river trying to drink it, which is really awful since he is suffering from a cold, and this what causes his own personal accident.
Animal Farm: Napoleon, Squealer, and their pig comrades are very gluttonous and very vile. They slack off, eat much of the food their fellow animals have worked hard to produce, murder anyone threatening their ill-gotten gains, lie about the conditions on the farm, and in truly awful moment sell the ever-loyal Boxer to a knacker, so they can buy beer.
The Dresden Files: Madeline Raith, a White Court vampire, is described as such, though without the physical gut. White Court vampires feed off psychic energy of an emotional state, with Madeline favoring lust. After years, maybe decades or centuries, of eating like this, it is second-nature to her. She walks through a crowd and one guy who got too close collapsed from her feeding off of him with no restraint. However, this has a drawback as even if she were to understand feeding off a person isn't smart, her inner demon and reflexes do it anyway. This is used to hurt her by getting a person protected by True Love, a Lust demon's bane, to touch her which leaves many burn marks on the vampire.