Most people love a good meal, but these gluttonous anime villains take it to the extreme. Majin Buu loves food so much that he transforms a whole city full of people into candy and devours them, while Rize Kamishiro of Tokyo Ghoul is known as the 'binge eater' for a good reason.
Some anime villains who eat a lot have expanded waistlines as a result of their constant snacking, but others are thin or muscular. In some cases, these characters are tough or hilarious, but in other cases, they can feel like offensive stereotypes. Whether you love these characters or hate them, they certainly make an impact.
As the homunculi representing the sin of gluttony, it would be surprising if Gluttony weren't deeply invested in eating. What makes Gluttony's appetite particularly terrifying isn't its expansiveness, although the sheer quantity is formidable. Actually, it's the fact that he happily chows down on human flesh, often specifically targeting his enemies. He also has the ability to consume materials that are usually not digestible, like steel, which makes it nearly impossible for him to be damaged by traditional weaponry.
Majin Buu loves eating, and he proves it by shooting a beam at his enemies that transforms them into candy and other tasty treats, which he joyfully consumes. He once did this to an entire city full of people, taking their lives in the process. This isn't because Buu is evil - it's because he doesn't understand the implications of his actions, and is focused solely on sating his childlike desires.
Like all ghouls, Rize Kamishiro survives by eating human flesh. But while most ghouls only eat what they need to to survive, Rize kicks it up several notches by binging on human flesh whenever the opportunity arises. Since ghouls have designated feeding grounds, Rize's appearance in any of them is a cause for concern, since she'll gobble up any person unlucky enough to be in the vicinity. This creates food scarcity and brings unwanted attention to her fellow ghouls, and it obviously puts human lives in peril.
While there are some exceptions to this, most Titans are eating machines who appear to have no purpose other than a relentless drive to consume human flesh. They don't appear to be doing this because of some kind of nutritional need, as Titans lack any form of a digestive system. When they run out of room, they vomit up the remains of their victims and run off to hunt for their next meal.