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The Blob, member of the Brotherhood of Evil Mutants. His weight and physical appearance are played up for horror and squick whenever he shows interest in a woman. In a bit of a subversion, his weight comes not from overeating but his mutation. When he was depowered, he ended up as his true weight - which was incredibly thin. After plastic surgery to remove his excess skin, he ended up being a pastiche of Jared from the Subway commercials. In the animated series and depending on the writer, he's still a greedy, slovenly, unhygienic pig, though. The animated series also tend to imply he is fat because of his eating habits.
Dialed Up to Eleven with the Ultimate Universe version of the Blob, to the point where he once paused during an attack on the Avengers Ultimates' mansion to raid the fridge. Less funny was the time he was discovered eating the Wasp's corpse.
Also from X-Men is the alien Mojo, a sort of fat evil television executive.
When Shadow King possessed Karma for several months in New Mutants, she became ludicrously bloated through Farouk's gluttony. She got better, thanks to the Desert Starvation Diet.
Whatever the explanation, it doesn't stop Spider-Man from going to town on him for it, at one point responding to being told that Kingpin was planning a huge operation using most of his available mercenaries by commenting, "Oh, he must be getting take-out."
Another example from Spider-Man's corner of the MU would be Nick Katzenberg, a Daily Bugle photographer and professional rival to Peter Parker. While not evil, Katzenberg was sleazy, immoral, and generally unpleasant.
Also in the Marvel Universe is the Slug; a drug czar who makes the Kingpin look svelte. He is so obese he cannot move without the aide of a motorized wheelchair and can suffocate people in the folds of his flesh. One source says he weighs 1,200 pounds. (Creator Mark Gruenwald remarked when the character debuted, "At the time, I thought a 1,200 pound man was a bit far-fetched, but I've since read about such a guy in People.")
This Trope is massively subverted by Big Bertha, a supermodel who has several 'brick' superpowers, including invulnerability and superstrength, and the ability to change shape but only into an obese (if she were not superstrong, she would likely be immobile) version of herself. Since no one recognizes the obese form as the same as her normal form, and in fact she only has the brick powers whilst in her fat form, she only fights crime as an obese person.
The cynical fatty tabby, Garfield. Other than abusing Odie and making his owner's life hell, he does nothing but eat and sleep.
Both Roark brothers in the comic version of Sin City are overweight and look unhygenic. Herr Wallenquist also has this look. They are all extremely evil crimebosses.
A lesser example would be Agamemnon, the sleazy porn-obsessed boss of Dwight and later, Wallace. He was an art dealer that was overweight, ugly, and smelled bad. He didn't pay well, either.
Subverted with Sam from Spawn. While he caters to every single characteristic of the trope, he's as good a guy as they come who always strives to right wrongs. The bastard tendencies tend to be directed towards bad guys. Clown (aka Violator), Tony Twist and Billy Kincaid, on the other hand, play this tropestraight.