Disney villains tend to be very noteworthy, both for their personalities and their songs. However, some of them can also be horrible, ruthless, and despicable. As Disney is primarily about kid-friendly fare, please note that qualifying for this trope takes something pretty extraordinary.
Disney Animated Canon
Atlantis: The Lost Empire: Commander Lyle Tiberius Rourke is a tomb-robbing mercenary, or as he insists "adventure capitalist", who's Only in It for the Money. What cements him is his attitude toward his current assignment. He takes the Heart of Atlantis, which is precisely what keeps the Atlanteans alive. Without it, they'll all die. Many other villains wouldn't be aware of this, and most would leave it once they learned that. Rourke, however, takes it knowing that the civilization will die, but his greed is so great that he doesn't even care. Later on, in order to ensure his escape, he throws his loyal Dragon off his ascending zeppelin. What settles his evil here is that he jokes about it, and caps it off with a "Nothing personal!" What's rather frightening is that it ISN'T personal; he hadn't had any problems with Helga beforehand, and betrayed her simply because it slightly benefited him.
The Lion King: Scar is defined by his envy and hatred of his elder brother Mufasa. Hating that he isn't king, Scar hatches a scheme to remove Mufasa from the equation as well as Mufasa's young son Simba. When Scar's first attempt to murder Simba and his best friend Nala fails, Scar has his Hyena cohorts cause a stampede and personally throws Mufasa in to be trampled when he escapes it. He then convinces Simba the whole thing was his fault, convincing him to go into self imposed exile before ordering the hyenas to murder Simba anyways. Scar's incompetence as king leads to a famine, and when Simba returns, he sees Scar refuse to allow anyone to leave to go anywhere else, declaring, "so be it" when Mufasa's widow Sarabi says he's condemning everyone to death. He proceeds to backhand her when she compares him unfavorably to Mufasa, and when he confronts Simba, Scar tries to break him by bringing up Mufasa's death. He only pauses in his attempt at a public execution to mock Simba that Scar was Mufasa's true murderer. Later, in a desperate attempt to save his own skin, he tries to blame everything on his loyal hyena henchmen.
Mulan: Shan Yu views the Emperor of China having built the Great Wall as both an insult and a challenge. As a violent Blood Knight, Shan Yu leads his horde of Huns to invade, relishing when China knows he's there. After capturing two Imperial spies, Shan Yu releases them with a message for the Emperor- but has one of his archers kill one anyways as you only need one man to deliver a message. Shan Yu later ambushes the armies of General Li at a village, resulting in a mass slaughter, not only of the soldiers, but every civilian as well, with no children spared either. Even after his army's downfall, Shan Yu attacks the Imperial Palace with his remaining men and takes the Emperor hostage, furiously trying to kill him when he refuses to kneel to Shan Yu.
Oliver & Company: Sykes is a disturbingly realistic villain for a Disney film. A loan shark who demonstrates his nastiness by rolling up his car window on the neck of a man who's late in his payments, Sykes has no hesitation releasing his savage attack dogs on the man's own pets. He later receives a phone call from a fellow mobster in the process of killing someone and gives the man advice on how to do it over the phone. Sykes later kidnaps a little girl to extort money from her parents and indicates he'll feed her to his dogs. When Oliver and team free her, Sykes unleashes his dogs after them and rides after them himself, fully intending to kill everyone.
Pinocchio: The Coachman is seemingly a kindly old gentleman, who kidnaps a bunch of troublesome boys who willingly went through with it so they could do whatever they wanted without adult supervision, and laces their cigars and beer with something that, when they act like jerks, turns them into donkeys he then sells as ordinary animals (one crate is even marked "SALT MINES". Considering the Real Life work conditions there, that's a Fate Worse than Death right there). From what he says to "Honest" John, he has been doing this for years, and the police have never caught him because by the time they arrive, the boys have all become donkeys, leaving no evidence that they were even there. The transformed boys who can still talk are locked up in a pen (it is unclear what becomes of them, though we're probably better off not knowing).
The Rescuers Down Under: Percival McLeach is a sick and twisted poacher. He starts by kidnapping Cody, a child who confronts him about his poaching, and then McLeach tricks the authorities into thinking Cody is dead by throwing Cody's backpack to the crocodiles. From there he tosses knives at Cody, locks him in one of the cramped cages he keeps the animals he's captured in, and to top it all off, ties Cody to a crane and lowers him into another river filled with crocodiles, only to raise him back up — then almost does it again just to toy with him. When the power on the halftrack goes out, stopping him from lowering Cody, McLeach takes out a gun and shoots the rope holding him above the river. Oh, and it is heavily implied that the reason he is a poacher is specifically that he enjoys hurting and killing animals.
Toy Story 3: Lots-O-Huggin' Bear allows the toys to be tortured by the too-young toddlers in the Caterpillar room, and will do anything just to keep his reign. Here's just a short list of his atrocities: lying to Big Baby and Chuckles that their owner had replaced them just so he wouldn't be alone in being lost, ordering the resetting of Buzz Lightyear, watching him beat down his former friends with a cold sense of satisfaction, beating Chatter Telephone to a pulp in order to find out about Woody's escape plan, and, in the climax of the film, he leaves Andy's toys to burn in the Incinerator after they risked their lives to save him, and he does so with a sadistic smile, a mocking salute and while yelling out "Where's your kid now, sheriff?". And while he does have a tragic backstory, there's a scene where Woody directly calls him out on how weak it is (his owner replacing him with a new Lotso was, considering she doesn't know toys are alive, a sign of how she loved Lotso; Woody says that it was Lotso who abandoned her). What makes it worse is there was almost no warning that Lotso was going to be the villain going into the movie. Sid and Stinky Pete to a degree had a glimpse of their villainy in previews but Lotso was promoted as a grandfatherly figure in trailers and commercials. Finally, he is the only villain in the franchise that never sought redemption. In fact, he only faked gratitude when Woody saved him, and ultimately he has gone down in the Pixar history as the most vicious villain that the company has created.
Darkwing Duck: Taurus Bulba, unlike the rest of the villains, has no ounce of comedy at all. Taurus had Gosalyn's grandfather murdered, and when he was trying to get the code for the ram rod, he threatened to drop Gosalyn off a building if Darkwing didn't get the code, he had no proof that Darkwing was told of a code, and was willing to try it, and when he was resurrected by F.O.W.L., he destroyed the place. All played completely seriously.
Gargoyles, for the most part, has a well-deserved reputation for sympathetic and three-dimensional villains - Xanatos pets at least as many dogs as he kicks, while Demona has an involved and tragic backstory that keeps her sympathetic despite the often extreme evil of her present appearances. There are, however, a few unrepentantly horrible ones:
Thailog is the Evil Twin of Goliath. Created from the DNA of Goliath, with some more from Xanatos and Mad Scientist Anton Sevarius, Thailog ended up as an Evil Genius whose only drive was his ambition to dominate, enrich himself and control what he could. Thailog seduced Demona and attempted to trick her and Macbeth into killing one another to steal their fortunes and seize control of their assets. He later revealed he had cloned the Gargoyle clan in preparation for killing them...even Demona herself. When Demona stopped Thailog from killing her daughter, Thailog merely attempted to kill her as well, and later resurfaced to gut Goliath with a knife to collect his DNA and potentially kill his 'father.'
Proteus of the New Olympians is a shape-shifting Serial Killer who was imprisoned after murdering the previous captain of the guard. He consistently assumes the form of his victim to mock the man's son Taurus. When he tricks his way to freedom, Proteus delights in sowing the seeds of chaos all through the city, using people's emotions against them with his powers for a sick thrill and trying to destroy his city and commit genocide on his own people.
My Babysitter's a Vampire: At first glance, Vice Principal Stern is just a Sadist Teacher, but that's just a cover for the genocidal wizard he is. Stern arrives in the town of Whitechapple to kill all vampires, even knowing that not all are evil, some of which are his students. He starts his plan by summoning the Breath of Death, a mist that drives vampires to kill each other, but that plan falls flat. Later he realizes that his non-vampire student Ethan Morgan is a seer and potential threat to his plans, so he attempts to kill Ethan, before later tormenting him with a hallucinations of his worst fear (of everyone being dead). He later steals a energy draining weapon called the Lucifractor and goes on a killing spree on the vampire council. He attempts to attach the Lucifractor to the Caller, a beacon of sorts for vampires, to kill vampires everywhere, and when Ethan tries to stop him, Stern casts a spell on Ethan's friend Benny to turn him evil.
The Lone Ranger: Butch Cavendish is one of the darkest villains to ever appear in a Disney film. Rumored to be a Wendigo for his unusual habits, Butch shows why when after gunning down the hero, Reid's brother, Butch cuts out his heart and eats it. Butch uses fear to oppress any hint of rebellion and will kill at any hint of complaint At one point, he even kills a laborer for nothing more than saying the entrance of a cave he wanted entry to was blocked. Butch conspires to start a war with, and wipe out the Comanche people for the silver in the mines by leading attacks on innocent people in settlements, framing the Comanche. In the past, when the Comanche saved Butch's life, he repaid them by slaughtering them, earning Tonto's undying hatred. With his evil and his dark habits, it's easy to see why Tonto sees Butch as a flesh-eating monster of myth.
1998's Mighty Joe Young: Andrei Strasser is an Evil Poacher definitely turned Up to Eleven and possibly even worse than Percival McLeach since he's played on more realistic levels. Killing little Joe's mother was just the beginning; he also did the same thing to Dr Ruth Young when she tries to save the little gorilla (it's uncertain if he did it on purpose, anyway he feels no remorse about it). He also owns a fake animal preserve while he actually secretly butchers endangered species and selling the animal organs off on the black market. This guy is so ruthless that even his partner in crime decides to quit when he arrives at trying to shoot Jill Young.
Lord Cutler Beckett of the East India Trading Company is the Big Bad of the second and third films in the trilogy. Upon his arrival at Port Royale, Beckett assumes illegal control and has the governor's messenger to the king murdered. Beckett later enslaves Davy Jones, forcing him to kill his pet Kraken and making Jones his personal attack dog of the seas. Governor Swann himself is later murdered when Beckett decides he's of no further use. It is made abundantly clear Beckett's prime control is power and control and piracy is a threat to that, particularly when he initiates a purge of anyone even vaguely associated with piracy with all legal proceedings suspended. The result is a massive line of people, many of whom aren't even pirates, taken to the gallows to be hanged. Not even children are safe as a little boy is shown being hanged as Beckett looks on without remorse or emotion. His only emotion is a satisfied "finally" when the prisoners indicate the pirate Brethren Court is going to be called.
Blackbeard from the fourth film is also an example: He enjoys torturing his prisoners, locks them in cages and burns them alive, punishes anyone who tries to disagree with him, his horrible treatment of Syrena, and in the end, he is ready to sacrifice his own daughter to save his own life. His disregard for his own daughter's life was even implied when he was ready to force Jack Sparrow to jump the gorge under the threat of her death, and ordered a mook to load two guns with a bullet each, and keep even himself in the dark as to which guns are loaded, and later lied to his daughter about knowing which ones are loaded.
Prince of Persia: The Sands of Time: Nizam, the uncle of the hero Dastan chafed at being in the shadow of his elder brother, the King. To remove himself from under the King's shadow, Nizam set his sights on the Dagger of Time and the Sands of Time, not caring of the horrors and chaos he could unleash on the world. Nizam brought about a battle with an innocent city, not remotely caring of the deaths of innocents, and arranged the death of his own brother while attempting to have his sons murdered. Revealing an utter contempt for the adopted low-born Dastan, Nizam revealed his true goal was to rewind time so he could undo this greatest error: once saving his brother's life when they were children.
Return to Oz: Princess Mombi somehow manages to outdo the Wicked Witch of the West in sheer unpleasantness: let's start with the asking price for helping the Nome King- the heads of several beautiful women. Mombi keeps these heads, still alive and still conscious, in a hall of cabinets; every so often, she'll "slip into something more comfortable" by swapping heads. And when Dorothy arrived in the Emerald City, Mombi had her imprisoned, fully intending to keep her there until she reached adulthood just so she could have a fully mature head to add to her "collection."
Who Framed Roger Rabbit: Ax-CrazyJudgeDoom is a shockingly dark villain for such a lighthearted film. Doom starts as a brutal, anti-toon bigot who invents a chemical called "Dip" that can destroy Toons, demonstrating it on an innocent little shoe Toon. Doom shows full willingness to kill or harm innocent humans, either himself or sending his toon weasel henchmen after them. It turns out Doom is responsible for the murder that has driven the plot, and the death of The Hero and private eye Eddie's brother as well. He also seeks to wipe out the Toon population with The Dip to profit off their destruction. What's worse is that Doom is a Toon himself in disguise, so he is engineering the destruction of his own species solely for his own greed and cruelty.
Kingdom Hearts: Master Xehanort is responsible, both indirectly and directly, for all the hardships the main characters suffer and the creation of the three main villains that are destroying the worlds. The secret reports in Kingdom Hearts: Birth by Sleep paint him as a well-meaning person ready to resort to extreme solutions of unleashing the Heartless and the Unversed in order to flood the universe with darkness and thus bring about perfect balance between light and darkness, but as of the game, he's clearly run so far beyond the line of inexcusable acts that any good intentions he once had are long gone. He takes Ven, an eleven-year-old child, in as an apprentice with the sole intention of training him to use the darkness and stealing his body. When Ven proves himself not to be up to the task, he forcibly extracts Ven's darkness, leaving him comatose, then drops his apprentice's failing body off in his own much-hated homeworld to die. After realizing Ven isn't going to die, he gives him to his fellow Keyblade Master Eraqus, a man whom he considers to be a brother, to train until Ven's light grows strong enough that he can be forcibly reunited with his darkness and become a weapon that will allow its wielder to reshape the entire world. While he's there, he notices Eraqus's student, Terra, and immediately decides that he wants Terra's body. Through a complex series of manipulations, Xehanort arranges Terra to fight Eraqus to the death, and finishes off Eraqus himself after Eraqus is weakened. He is even willing to risk an apocalypse out of sheer curiosity. Eventually Xehanort willingly splits himself into two beings: his Heartless, "Ansem", which possesses Riku and manipulates a cartel of Disney villains from behind the scenes, and his Nobody, "Xenmas", which formed Organization XIII, manipulated its members to stop them from growing Hearts for themselves, and planned on using all of them as vessels to store pieces of his own Heart in, to turn them into clones of himself.