Vile Villain, Saccharine Show

"Shan Yu, one of the most badass Disney villains ever. That dude was a monster. In fact I kinda felt like he was out of place in the movie because Mulan is overall is kind of a silly movie. And then you have this big grim beast of a man just fuck'n shit up."

- the1janitor

Okay, so you have a villain, who is legitimately intimidating and frightening. Maybe he tries to destroy all positive emotions, or maybe he turns people into twisted shambling abominations, or maybe he's plotting genocide. Point is, he's actually a fairly creepy villain. The irony is that he's stuck in a Sugar Bowl.

As one could probably tell, this trope is about villains in normally lighthearted fiction that are so disturbing, or even terrifying, on some level that they kind of clash with the tone of the show/game/whatever. Because of this type of villain's ability to ruin the mood of the story he/she/it is in, this trope can overlap with Complete Monster and Knight of Cerebus. If a series has a lot of villains like this, then it's taking a ride on the Cerebus Rollercoaster.

A major cause of Sugar Apocalypse and Surprise Creepy. Compare and contrast the Crap Saccharine World, where it's not just the villain, but the entire world that is rotten to the core.

Anime & Manga

 * Mon Colle Knights is cheerful and wacky and the enemies usually are the Terrible Trio. When they're not, there's Reda, with his bloodstained wings and a fondness for driving people to suicide and subjecting things to splooshy transformations. The english Gag Dub toned him down and edited some scenes.
 * The usually light-hearted Pokémon anime (which normally has a goofy and incompetent Terrible Trio composing of two delinquents and a talking Meowth as the primary antagonists) has:
 * The coldhearted Diabolical Mastermind, Giovanni, and the psychic Gym Leader with a split personality, Sabrina, in the Kanto Saga.
 * The merciless Pokémon Hunter J, the Omnicidal Maniac Cyrus, and the abusive Jerkass trainer Paul in the Sinnoh Saga.
 * Complete Monsters, the Iron Masked Marauder and Kodai, in the fourth and thirteenth movies respectively.
 * Oh, and as of the recest iteration, Best Wishes? The goofy, incompetent Terrible Trio isn't so goofy and incompetent anymore....
 * The Bigger Bads in Pretty Cure franchise are usually like this. One of them is an entity that existed before everything and wants to plunge everything into nothingness, another is a life-hating Eldritch Abomination that turns every planet he visits into sand dunes, yet another is a monster born out of humanity's collective negative emotions, etc etc... Mind you, this is a series that is (supposedly) for little girls in elementary schoolyears.

Comics

 * Parodied in Steph Cherrywell's Widgey Q Butterfluff, with Lord Meanskull and his Hench-Witches.
 * Les Légendaires is a seemingly kid-friendly comic book, involving a world where everyone has been turned into children following a magical accident. The characters are typically comical (though they do have moments of Badass), and the universe even more. But let's have a look at the main villains:
 * Darkhell is a homicidal, megalomaniac, cruel Evil Sorcerer (and formerly Sorcerous Overlord) who made insane experiments, was The Dreaded for years in his world and cause a large amont of death each time he shows up. While he was scary already as an adult, having turned back to childhood only makes him more disturbing.
 * Skroa is a bird-like demonical sorcerer that used to be Darkhell's rival and frequently uses the protagonists as pawn for his plans. Is shown slaughtering a group of armed human beings of his own. Not to mention he once cut his own arm off as a part of his plan;
 * Anathos is basically this universe's version of Satan, being a Magnificent Bastard and Omnicidal Maniac God of Evil that actually succeeded in destroying the world long time ago and almost succeeded a second time. The fact he came back by reincarnating in one of the protagonists and litterally crushed the remaining heroes in their first fight, leaving them scarred for life, makes it worst;
 * Abyss; O God... the character is introduced as seemingly extremely nice person in his first appearance, only to be revealed later as a Complete Monster Yandere (disambiguation) who seems to have a thing for his foster sister, to the point of forcing her to joing his side by brainwashing her through Puppeteer Parasite.

Films -- Animation

 * Were Back a Dinosaurs Story is a cutesy film about dinosaurs being sent to our time to make children happy. Nothing scary about that at all. Well, except for the creepy old scientist Professor Screweyes, who runs a Circus of Fear, believes that the world is an irrational and cruel place, got his eye pecked out by a bird, and was eaten by birds at the end of the film.
 * The Disney Animated Canon has a disturbingly/wonderfully high occurrence of this trope:
 * Maleficent from Sleeping Beauty.
 * The Disney version of Claude Frollo from The Hunchback of Notre Dame is, for all intents and purposes, a medieval stand-in for Hitler. The movie was already more adult than is normally thought of for Disney, but it was still shocking.
 * More disturbingly, Claude Frollo is one of the most realistic Disney villains ever produced, and he doesn't have an iota of comedic qualities. And people like him existed in reality. There's a reason why many see him as the darkest villain the company has ever made.
 * The evil Queen from Snow White and The Seven Dwarfs is pretty damn creepy. A woman so obsessed with her own beauty that she's willing to let a teenage girl die for being pretty? Yikes. The fact that the teenaged girl is also her step-daughter? Double yikes. Going so far as to painfully transform herself into an ugly old witch to trick the teenage girl so she can poison her? Yikes to infinity.
 * The Princess and the Frog gives us Dr. Facilier, a voodoo witch doctor willing to sacrifice all of New Orleans to pay off his debts to dark voodoo entities. Although he gets in on the light, jazzy theme of the movie with a heck of a cool Villain Song, it's still clear that he's selfish, relentless and bad to the bone. The fact that he cements this.
 * A lesser known example is the Coachman from Pinocchio, who runs an amusement park that magically turns young boys who use the attractions into donkeys. The ones that lose their voices are then sold to salt mines and circuses, and the ones who can still talk... well, they're put in cages, and we don't know what happens to them after that. It seems that none of them are ever human or see their homes again, though. And he gets away with it, too! Which is unique, considering just about every other villain falls to the hero.
 * This may be because of his choice of targets: Bad boys who should be at school, making him some karmic bogeyman.
 * Though the Coachman is far worse, Stromboli is pretty bad too.
 * Oliver and Company is a very lighthearted movie, featuring talking cats and dogs. Its villain, Sykes, is a Loan Shark who is played utterly straight. There's nothing cool, funny, sympathetic, or even hammy about him. He's just a cold-blooded thug who wants his money now and doesn't care what he has to do to get it.
 * Though not as frightening as Frollo or Maleficent, Jafar in Aladdin has shades of this. Because the movie was an action-packed zany comedy, animator Andreas Deja decided to keep Jafar very subtle in contrast. (He also contrasts the art style. Nearly everything else in Agrabah has soft, rounded lines, while Jafar has several sharp angles.)
 * Mulan is the story of a girl who goes into the army to save her father's life. While the movie is comedic much of time (and even has a non-threatening dragon voiced by Eddie Murphy and a cute little cricket), the Big Bad Shan-yu is implied to kill vast numbers of people. The aftermath of his handiwork makes a Mood Whiplash from a song about getting a girl to seeing the most straightforward example of War Is Hell in a Disney movie. The scene with the destroyed village also has a subtle implication that the Infant Immortality was averted with the appearance of a doll without its owner.
 * Professor Ratigan of The Great Mouse Detective, who spends most of the film as the epitome of the Faux Affably Evil, Evil Is Hammy villain (helped by being voiced by Vincent Price, who is very obviously really enjoying himself), so it's easy to forget that he kidnaps frightened children, has no qualms about threatening them or getting them killed, and a throwaway line in his Villain Song refers to "those widows and orphans you drowned". Then his temper gets pushed that little bit too far, and... Holy Shit.
 * One Hundred and One Dalmatians has Cruella DeVil, who for all her campy vampiness, her basic goal is still to kill and skin a bunch of puppies to make them into fur coats.
 * Scar, from The Lion King. Simply put, he gets the honor of committing the first onscreen murder in a Disney film.
 * In a (semi) Live Action example, Judge Doom from Who Framed Roger Rabbit. The film initially seems like a classical Family movie until we meet him. We discover that not only is the responsible of all bad things that happen in the movie.
 * Toy Story is a lighthearted series where the main conflict is usually within the heroes as opposed to external. Villains tend to be either Obliviously Evil or relatively harmless. Until Toy Story 3, that is, where we meet !
 * Hopper in A Bugs Life is a ruthless tyrant who delights in the fear he instills in the ants, and was fully prepared to publically execute their queen to keep them compliant. He even admits to his minions that they don't even need the food the ants provide, implying his actions are motivated purely by sadism.
 * in Up is a delusional and sociopathic murderer who kills anyone who he even thinks.
 * Little Nemo Adventures in Slumberland has the Nightmare King suddenly show up in a world that was just plain Sugar Bowl till then, ruling over a section of Slumberland known as Nightmareland, the place where nightmares come from.
 * Osmosis Jones: For the most part a lighthearted parody of Salt and Pepper cop movies with copious amounts of Toilet Humour for the kids all set inside the human body. Enter Thrax, a Complete Monster who kills cells by making them melt and explode via fire from the inside out, and we learn his goal is to kill his human host, which in this context would be like an alien arriving on Earth and trying to destroy it For the Evulz. He counts his victims on his fingers at one point in the movie, one of them being "A child who didn't wash her hands like she was told."
 * Kung Fu Panda 2 has Shen, an evil peacock tyrant who is bent on destroying kung fu with heavy artillery, terrorized many innocent pigs and bunnies with his army of wolves, and he even almost pushed the entire panda species (which includes Po) to the point of extinction! All of this is enough to make Tai Lung, the snow leopard villain of the first Kung Fu Panda film look like a scaredy-cat.
 * Some of the villains from the later Don Bluth films, including an evil owl sorceror who hates daylight, wears an opera cape and a monocle, and for some reason breathes Lucky Charms; an evil, fat troll queen who hates both nature and New York City; an evil penguin voiced by Tim Curry, and an evil, undead Russian necromancer. Even less so with his earlier films, whose villains include an evil rat, a ferocious green Tyrannosaurus Rex with razor-sharp fangs and blood-red eyes, a mean cat with a gold tooth, and a canine crime boss.
 * The Brave Little Toaster is a cute musical film about talking electrical appliances, but then we meet the Junkyard Magnet...
 * SpongeBob SquarePants was a lighthearted series with an Ineffectual Sympathetic Villain. Then The Movie comes out, where we're introduced to Dennis, a somewhat comedic but still surprisingly terrifying hitman wanting to KILL Spongebob and Patrick using sharp spiked boots. Also, Plankton turns out to be Not So Harmless, framing Mr. Krabs for stealing Neptune's crown and getting him frozen, then later coming back to see Mr. Krabs get burned to death. If that's not passing the Moral Event Horizon, brainwashing and enslaving all of Bikini Bottom certainly qualifies, especially since it's implied that the fish that were wearing the bucket helmets were awake and conscious while under control!
 * Also in The SpongeBob SquarePants Movie, there's the cyclops diver, who captures sea creatures and painfully kills them using the heat of a bright lamp, then he sells them as knick-knacks.
 * Despicable Me has Miss Hattie and  Although Big Bad Wannabe Vector ended up getting some punishment of some sort, these two both manage to get away with everything!

Literature

 * Charlie and the Great Glass Elevator, by Roald Dahl, has the sudden intrusion of a Horde of Alien Locusts into an outer space sequence that until then is mostly whimsical.
 * Redwall; it seems like a happy fluffy world full of cuddly talking animals. Then you meet the villains, who get their own Complete Monster page.
 * Tove Jansson's The Moomins take place in Moominvalley which is, at least at a very quick glance, somewhat of a saccharine world in the early novels and some of the adaptations. Then we are introduced to the Groke who, especially in her earliest appearances, is truly horrifying.

Live Action TV

 * Even though Seinfeld is not exactly a cheerful show (it's actually quite cynical), Joey "Crazy Joe" Devola still adds a surprising dash of darkness to it. If Elaine continued dating him past the episode "The Opera", he probably would have been a full-fledged Token Evil Teammate.
 * An in-universe example appears on Star Trek: Voyager with the Show Within a Show The Adventures of Flodder, a series of fantasy holonovels for children. One of the titular adventures involves a character called the Ogre of Fire, who shows-up, vaporizes the main character in front of the child's eyes, and then torches the setting to the ground.
 * Yogoshimacritein in Engine Sentai Go-onger. Not only is he more evil than his son, but he's also a very Bad Boss, . He also has access to a device that deletes people from existence.
 * Kamen Rider Fourze--a High School version Kamen Rider penned by the same guy who made Gurren Lagann--seems cheerful, right? Wrong. The monsters, known as Zodiarts, are actually fellow students--many of them having lots of psychological issues--alongside the teachers who actively are giving them the means to become evil.

Theatre

 * Arsenic and Old Lace is mostly a lighthearted "comedy of murders", but more or less treats the character Jonathan Brewster as a completely serious and frightening villain. He's indicated to be a prolific murderer with a love of torture, and it's clear that he's been this way since he was a child, since his hobby then was torturing his brother by putting needles under his finger nails.

Video Games
"The Sorceress: What did you think I was going to do with all those eggs? Put them in a zoo?
 * The Kirby series is set in a Sugar Bowl. The main villain, Dark Matter, is an Eldritch Abomination who appears in a multitude of disturbing forms. These include Zero from Kirby's Dream Land 3, the boss of Dark Matter who cuts its own iris and bleeds as an attack, and later it rips its own iris out. It is reincarnated as 02 (pictured) in Kirby 64, a creepy angel thing with a blood-dripping eye.
 * Another is.
 * Kirby Mass Attack has Necrodus, the monster that split Kirby into ten pieces, and the Skull Gang, his minions.
 * It's been pointed out that very disturbing final enemies make a great deal of sense in Kirby: he lives in Dream Land. What would be the villain of Dream Land other than something out of a nightmare? One of them is even called "Nightmare".
 * Earthbound combines this with Mood Whiplash, in the final fight, in what had started as a funny and lighthearted game, with Giygas, a horrible Eldrich Abomination with more than a few similarities to Azathoth that you cannot defeat in the normal manner and whose attacks are so powerful your mind cannot comprehend them,
 * In Mother 3, there's, who
 * in Disgaea 2: Cursed Memories even has her own ominous leitmotif. She's made even more horrifying in the infamous worst ending,
 * While Amateur Surgeon is not exactly saccharine, is still pretty light, with Black Comedy and friendly criminals. Then we have the Big Bad,, a frighteningly evil madman who had tried to get Aureola and Dr. Bleed killed, and given Alan hell throughout the entire story.
 * NiGHTS Into Dreams has a relatively cutesy and bright-colored aesthetic to it (much like Kirby, but to a lesser extent), but the bosses, in addition to being (arguably) the most difficult parts of the game are Eldritch Abominations. that look like something out of a Tim Burton movie.
 * All the Mario villains appearing in the RPGs. You've got the Omnicidal Maniac of Dimentio in Super Paper Mario, the super-creepy Cackletta in Mario & Luigi: Superstar Saga, the weapons crazed Smithy in Super Mario RPG, the force of evil that's Dark Star in Mario & Luigi: Bowser's Inside Story, the demonic Shadow Queen in Paper Mario: The Thousand-Year Door, the invading Shroobs in Mario & Luigi: Partners In Time... That's a fair amount of disturbing villains in the otherwise quite light-hearted series.
 * Smithy in particular set the standards as the villain of the first Mario RPG. After traversing the Mushroom Kingdom which as to be expected is bright, colorful and full of wacky and strange enemies...you find the portal to Smithy's realm and find it a dark, gloomy, mist-covered factory full of machines and ghosts.
 * Hell, Arch Enemy Bowser sometimes counts underneath all the ham. He is Great Demon King Koopa after all, and can cause major damage when he's actually trying. He tries on two separate occasions to remake the universe in his own image, which is exactly what Dimentio wanted to do, but old Bowser did it by stealing from God with nothing but his Airship fleet and his army. Dry Bowser is him resurrected as a huge demonic skeleton. And of course, there's Giga Bowser....
 * Cave Story is a pretty cheery-looking game with Ridiculously Cute Critters, a Quirky Miniboss Squad with a memorable Catch Phrase and a main character who's pretty much Badass Adorable incarnate. And you're facing a Mad Scientist who is irredeemably evil.
 * It gets even creepier when you enter the Brutal Bonus Level.
 * , the main villain of the Pokémon Mystery Dungeon series games. Prior to the second game's events, he steals artifacts responsible for the balance of the universe as an attempt to destroy both space and time and in the process, he makes one of the gods evil and crazy, then he wipes the hero(ine)'s memory clean and turns him/her into a Pokémon. Later, when this doesn't work, he decides that the easiest way to get rid of his aforementioned archnemesis is to make him/her commit suicide!
 * Not to say the main games aren't proofed against this trope, either. On one hand, you have Ridiculously Cute Critters in beautiful grassy fields. On the other, Jerkass rivals, mafia goons, emotionally repressed (and hateful of living spirit in general) Cyrus, extremely misanthropic Purple Eyes, notorious childbreaker Ghetsis, and the cabinet of mindrapist abominations known as Cipher.
 * The Spyro the Dragon series takes place in a dreamlike environment with mostly cute characters...but occasionally has genuinely creepy enemies. The Dark Passage level from the first game is rife with these as is Haunted Towers. The Metropolis level from Spyro 2 is a rather jarring break in an otherwise cutesy game, with its psychotic cows in space suits who stare angrily and shoot you, as well as exploding pigs who come flying at you out of nowhere (and they will always hit you unless you kill them first). The robotic sharks in water levels are horrifying, especially when you try to go in there without a submarine (you are killed instantly). And also there are levels where plants can eat you. There are quite a few bosses who are pretty unnerving as well.
 * The Sorceress in 3, who steals all the baby dragon eggs because  Scorch, the 3rd boss, is pretty damn creepy as well, being solely created for the purpose of brutally murdering the heroes.
 * Granted the manner the Sorceress reveals her evil plan fails to be that terrifying at all...
 * Mook in the background giggles quietly*"


 * Wario Land 3 has enemies and bosses typical of the series... and then there's Rudy the Clown, who turns this Up to Eleven via Interface Screw and sudden subversion of a core game mechanic. Not only is he a powerful demon (blood-red teeth and Evil Laugh not shown), but he's the only thing in the game that can actually kill Wario, and the game auto-saves if he does.

Web Comics

 * The entire point of Hello Cthulhu.

Web Original

 * Most Neopets villains are Laughably Evil, but plot villains tend to be really, REALLY EVIL.
 * Much of the time, Suburban Knights has the same tone as the rest of the That Guy With The Glasses site; definitely not for children and sometimes resorting to Refuge in Audacity, but still comical and not taking danger very seriously. However, this doesn't hold true when Malachite - an apparent complete sociopath who murders multiple innocent people just for using technology - is on screen. While most of the site's villains are Played For Dark Comedy, Malachite is almost always Played for Drama.
 * Another unusually serious villain for the site is The Entity from Atop the Fourth Wall. This may be because it's an Eldritch Abomination that tries to destroy the universe.
 * Reflets D Acide, is a fantasy Affectionate Parody with comical characters, but antagonists Belial and Alia-Aenor, while both having comical moments, are actually threatening villains, with Belial possessing a Complete Monster status and Alia-Aenor being a Bitch in Sheep's Clothing.

Western Animation

 * Care Bears, of all franchises, tends to have this in spades, what with Professor Coldheart, the Spirit in the Book, Dark Heart, No-Heart and others all dedicated to the removal of any ability to feel emotion.
 * The New Adventures of Winnie the Pooh episode Cleanliness Is Next To Impossible where a creature named Crud (voiced by Jim Cummings using his Robotnik voice from the Sonic the Hedgehog SATAM show) imprisons Pooh, Piglet, and Tigger and then tries to force Christopher Robin to help him make the rest of the world dirty by saying "If you don't, YOU'LL NEVER SEE YOUR FRIENDS AGAIN!". Granted, by normal standards this hammy cartoon blob is not much worse or creepier than most Disney Afternoon villains, but he's much more so then you'd expect from one of Disney's lightest and softest universes.
 * Prior to New Adventures the inclusion of any villains period was completely new to the franchise, which usually didn't have any antagonists (par maybe Rabbit, which still isn't saying much). For example this was the first depiction to show real Heffalumps and Woozles. Granted they were all comical and almost as hapless as Pooh himself, but were still a big change from the usually laid back stories of A A Milne's creation.
 * My Little Pony has such characters as Tirek (a demon centaur who wanted to turn the ponies into an army of demonic dragons with his "Rainbow of Darkness"), Katrina (a catwoman sorceress who plotted to enslave the ponies into gathering ingredients for her Fantastic Drug of choice, "witchweed potion"), Squirk (a tyrannical sea monster who wanted to reclaim part of his undersea kingdom by flooding Dream Valley), and The Smooze (an all-consuming blob monster unleashed by a Card Carrying Villainess and her bumbling daughters). The G1 continuity has a lot of villains who came close to enacting a Sugar Apocalypse.
 * Crunch the Rock Dog, a huge dog made out of stone that hates all things soft, and has the power to turn anything he touches to stone, and turn normal rocks into sharp-toothed monsters to stalk his prey. The way he and his rock minions chased after the Bushwoolies, turning them to stone one by one, seems right out of a horror movie.
 * While most villains in the series turned good or simply fled when defeated, two of them (the aforementioned Tirek and the magma-creature Lavan) were so evil and powerfull that the heroes actually had to kill them. This is notable not only because a series based on something as innocent as the My Little Pony toys would probably be the last place anyone would expect to see someone die, but also because characters being killed of was something very rare to see in any TV cartoon in the 1980's.
 * The G4 series, My Little Pony Friendship Is Magic, has Nightmare Moon, sister of Princess Celestia who, in a fit of envy, plotted to bring about The Night That Never Ends (which according to Word Of Faust would have killed all life in Equestria).
 * The Parasprites. Although not so much villains as an unrelenting all-devouring force of nature, their consuming pretty much the entirety of Ponyville in the span of a couple minutes is pretty chilling.
 * Discord, a trickster spirit with a warped sense of humor. Despite his comical mix-and-match appearance, and his first evil act being generating clouds of cotton candy that rain chocolate milk, he turns out to be a formidable foe. Screwing with the heads of Twilight's friends he effectively destroys their connection to their respective Elements of Harmony, all but completely eliminating their only chance of beating him, and subsequently turns Equestria into a realm of madness and chaos where gravity, time, and even basic causality have all taken an extended holiday.
 * "Hearth's Warming Eve" introduced the Windigos, evil spirits who feed off of hatred and cause deadly blizzards. They drove the original ponies from their homelands, and nearly destroyed Equestria. Moreover, it's implied that they freeze people in a state of hatred but keep them alive so that they can have a continuous food supply.
 * "A Canterlot Wedding" has who, and launches a full scale invasion of Equestria, complete with terrified ponies desperately fleeing from her minions.
 * The Powerpuff Girls
 * Him, one of the scariest (and daring) villains on a Cartoon Network comedy ever, even turned Townsville into a living hell on earth when the girls accidentally traveled forward in time.
 * A soundalike bear from The Teletubbies must be also vile out of universe.
 * At least Him has comedic traits. Dick Hardley, however? Dear GOD.
 * Father from Codename: Kids Next Door. A shadowy figure with control over fire, who brainwashed five children into thinking they were his/being evil? Add that to the fact that he is always beaten by the skin of everyone else's teeth and you've got a very threatening villain for such a harmless show.
 * And then once Father went through massive Villain Decay, The Movie gave us Grandfather, Father's father, who possesses many of Father's abilities as well as the ability to turn all the people in the world into undead senior citizens.
 * Sideshow Bob from The Simpsons has always been distinctly darker than anybody else in a cast of hundreds. Especially prevalent in the classic "Cape Feare" episode where he forgoes evil plans and just tries to slice Bart to pieces with a machete, crouched and approaching with dark rings under his eyes...
 * Perhaps to balance it out, the Sideshow Bob episodes were also frequently Denser and Wackier, even during the show's earlier more "down to earth" depiction. In the same above stated episode, Sideshow Bob was driven through a cactus patch, walked through a pile of rakes and trampled by circus elephants. He later sings the entire score of H.M.S. Pinafore as a final wish to Bart before attempting to murder him (complete with makeshift props, costumes, an issue of Playbill with his picture on the cover, and a giant Union Flag unfurling behind him during the grand finale).
 * While a few of them do play nice, most of the diesel engines in Thomas the Tank Engine are very vocal about their desire to overtake the steam engines and aren't above trying to hurry that day along. At least twice, they've tried to smelt down other engines and escaped any consequences.
 * Phineas and Ferb is a show that invokes Rousseau Was Right and usually has a Ineffectual Sympathetic Villain, which makes the presence of the unnamed Drill Sergeant Nasty in "Phineas and Ferb Get Busted" all the more surprising. He spends the entire episode coldly and sadistically pounding out any creativity and happiness from the duo. He even He's also, so the show can get away with this.
 * Cracked.com presents: 7 Badass Cartoon Villains Who Lost to Retarded Heroes.
 * Teen Titans sometimes has this trope. The show itself is usually lighthearted, and most of the one-shot villains are comical (with a couple of notable exceptions)- but lets take a look at some of the Big Bads. Slade is a creepily emotionless diabolical mastermind who pretty much runs on blackmail, Mind Rape, Hannibal Lectures and Foe Yay, and delivers No Holds Barred Beatdowns to several characters in surprisingly vivid fashion. Then there's Trigon, who's basically Satan and wants to use the show's main Woobie, who's also his daughter, to bring about The End of the World as We Know It- and he actually succeeds in causing Hell on Earth for two episodes. Fun times.
 * Both villains (as well as Brother Blood) were toned down a lot for the cartoon. For much of the '80s, the Teen Titans was one of DC's darkest books. The fact that they were able to make it a kids' show is a feat for the ages.
 * Adventure Time is more of a Crap Saccharine World than a saccharine one (though the characters inside don't seem to care), but most monsters encountered are easily defeated and the common recurring enemy is an Ineffectually Sympathetic Jerkass Woobie, making Marceline's dad and The Lich still terrifying regardless of all the other nasty things lurking about.
 * The Transformers Animated version of Megatron, given the show's colorful and cartoonish nature.
 * Shockwave, who murdered in an incredibly horrifying manner, Wasp, being in a continuity where his insanity isn't played for laughs and is completely terrifying for it, and Lockdown, a freelance assassin Transformer who's caused Ratchet to have war flashbacks.
 * Lockdown's whole body is a Swiss Army Weapon whose left arm and leg don't match his right. Why? He butchers other Transformers for their parts to increase his power.
 * Prometheus Black/Meltdown is a rare human example in the series. While the other human villains in Animated are deliberately used as filler and to exemplify the Decepticons as a greater threat, Meltdown manages to be geuinely depraved and terrifying. Case in point - in his second appearance, he was experimenting on humans to try and create human transformers (he'd already done at least two adult humans, one of them his former lawyer, and was planning to use 8-year-old Sari Sumdac as his next test subject).
 * The Classic Disney Shorts have The Mad Doctor, who is an evil doctor bent on cutting up Mickey's dog Pluto as part of a lab experiment. Later, he actually threatens to cut open Mickey Mouse himself! Fortunately, he only exists in one of Mickey's nightmares. And because he is so evil, his picture is even placed on the Complete Monster page for the Disney villains!
 * Zordrak of The Dreamstone. A gargantuan bellowing Eldritch Abomination with a serious Hair-Trigger Temper that frequently abuses or even exterminates his Slave Mooks the Urpneys for the slightest irritance. While also managing to be rather funny, he's a pretty creepy guy, even when not compared to the cutesy residents of the Land Of Dreams.
 * Gargamel of The Smurfs qualifies for this designation, though not always.
 * Dr. Blowhole in The Penguins of Madagascar. In his debut episode he planned on flooding the world, just because of all the embarassment humans put him through when he was a circus dolphin. And in his second appearance, he intentionally meant to drown Skipper when he gave him amnesia. And that, after his first appearance, some of the other episodes went through Darker and Edgier territories.
 * A Finnish Children's show called The Moomins stars a family of cute claymation hippos--occasionally visited by some void/plague/death incarnation that can apparently kill things just by standing near them. It also moves like some kind of demon ghost.
 * Ed, Edd n Eddy has Eddy's brother. Sure, the show itself was a Sadist Show, but everything that happens to the Eds up until his appearance is played for laughs and could be considered lighthearted enough. Come the end of the movie, this guy manages to genuinely harm both his own brother and Edd, and he's been abusing the former for years. What all the typical bullies in the show witness him doing is horrific enough for them to redeem themselves and accept the Eds as their friends once and for all.
 * XANA from Code Lyoko: the show takes place in a college that appears to be a rather light-hearted, comical setting, with a ridiculous gym teacher, a Lovable Alpha Bitch and characters making jokes, but as soon as XANA starts acting, we suddenly get stuff such as Killer Wasps/Rats/Birds invasions, Giant Destructive Teddy Bears, place where Everything Is Trying To Kill You, Zombie Apocalypse, cataclysms, Demonic Possession, and the list goes on.
 * Dora the Explorer normally only has Swiper, but some of the movie Big Bads qualify. Especially the Witch from "Dora's Fairy Tale Adventure", who put Boots in a never ending sleep For the Evulz and was genuinely evil.