Be Prepared from The Lion King is unarguably one of the best, if not the best. Just to drive the point home, the chorus of hyenas backing Scar through this song up march in formation at one point, in a manner based on footage of a real-world Nazi rally. Furthermore, most Villain Songs involve the villain's evil laughter at the end. This one trumps them all, with not just Scar and his Terrible Trio laughing, but about 200 OTHER hyenas joining in with them. Just take a look at the original English version
"Be Prepared" originally had a reprise that was cut from the final film, that was to be sung as Scar took the throne. See it here
Also worth noting, is this one was primarily for the Hyenas, as it was their introduction to the pride and they have far more lines than Scar.
That clip is actually taken from a much longer cut scene where Scar decides to take Nala as his queen and informs her through a slightly salsa-like variation of Be Prepared. After she slaps him mid-song, he decides to banish her from the kingdom. (cue the above reprise)
"Prince Ali(Reprise)" from Aladdin. In fact, there were 5 separate songs made for Jafar and all but one were cut. Humiliate the Boy where Jafar does what the title suggests (cut for being too caustic). My Time Has Come where Jafar recounts how hideous his life has been and how he is going to make everyone else miserable (cut for being too slow and introspective). Why Me was basically the same as My Time Has Come (cut because the directors felt it didn't advance the story enough, they also wanted something with a big chorus; kept in the musical adaptation). And My Finest Hour where Jafar pulls the earth into a ball and bats it around with the Genie (cut because the directors decided it was too late in the movie for an extended showstopper for the villain). Instead, the "Prince Ali (Reprise)" is a trim ditty that makes dramatic sense with Jafar turning Aladdin's entrance song into a sweet revenge where the sorcerer revels in having the upper hand.
The workshop tapes for the stage version have TWO more songs for Ursula: "Wasting Away" (bemoaning her current dreary, thin and emaciated [she thinks] state), which was replaced by "I Want the Good Times Back", and "All Good Things Must End" (where she gloats over the frailty of happy endings).
"Les Poissons" is also from The Little Mermaid. Although Louis isn't a flat-out villain, he does try to kill Sebastian, and the song is certainly sadistic enough to qualify.
"Gonna Get My Wish", a deleted scene from the sequel. This song is so awful it's no wonder it was deleted from the film, and it's all the more tragic when you remember Morgana's voice actress is the same as Ursula's and that her talents are being completely wasted.
Headless Man from The Legend of Sleepy Hollow is sung by Brom Bones about the Headless Horseman, but because some suspect him of being the Horseman...
It was subtle enough that most kids didn't get it until they were older, though the image of Esmeralda in the fireplace and the monks in red cowls were amply terrifying nonetheless.
"Hellfire/Dark fire/Now, gypsy, it's your turn/Choose me or/Your pyre/Be mine or you will burn". It's a Dark Reprise of the opening song, "Bells of Notre Dame", and it comes right after Quasimodo sings his own song about how he's fallen in love with Esmeralda (Heaven's Light).
It's particularly chilling because, unlike most Disney villains, Frollo doesn't even begin to think he's bad. He think's he's probably the holiest person in all of Paris. He fully believes that his lust is her fault because she's literally the devil. He's not only evil - he's deluded and scared and angry, as opposite to the usual gloating most villain songs exhibit.
Consider that Heaven's Light and Hellfire are actually one continuous piece, and that both are about how the singer have fallen for Esmerelda. Also consider that the two songs are bridged by priests singing the first few lines of the Confiteor, a Catholic prayer for confession of sins, and that excerpts of the Confiteor are used as Ominous Latin Chanting during Hellfire, whose main lyrics are Frollo's way of saying that he's above everyone else and that his lust isn't his own fault. There are a lot of things that make Hellfire work.
Court of Miracles from the same film has lyrics and sinister visuals worthy of a Villain Song, so it deserves a honorary mention, even if it is actually sung by Clopin, who thinks Quasimodo and Phoebus are working for Frollo.
In the stage version, "Me" and "Maison des Lunes" (the latter comes when he plots to institutionalize Maurice) also qualify as these. "Me" is an example of the unconscious villain, as it's Gaston stating the facts of his little universe - which are that he's the best and he deserves his dreams to come true, because he's every woman's dream. "Maison des Lunes" is more straightforward, in that it involves wrongfully imprisoning a weak old man so Gaston can marry his willful daughter — and relishing every minute of it.
Gaston: Yes I'm endlessly, wildly resourceful... Lefou: As down to the depths you descend! Gaston: I won't even be mildly remorseful... Both: Just as long as I (you) get what I (you) want in the end!
It's also a bonus in the Australian version because he's played by Hugh Jackman (who played Wolverine in the X-Men movies).
The original version of The Gaston song has the additional part at the end where Lefou tries to spell Gaston's name but gives up.
Beauty and the Beast: The Enchanted Christmas has an arguably better Villain Song. The Royal Court Composer, Maestro Forte, who was changed into an Ominous Pipe Organ from the enchantment and wanted to stay that way, sings "Don't Fall in Love" in order to dissuade Beast from having any feelings for Belle. Oh, and this is another one like Hellfire in some of its lyrics; just be glad that kids can't listen or understand it as well as they can when they're older.
You'll go to pot, You'll turn to drink, You'll never rest, You'll end up mad And looking like some poor demented dove! Don't Fall in Love!
"Mine, Mine, Mine" in Pocahontas, at least the parts that aren't sung by John Smith. "Savages" is a half-example, as part of the song is sung by the villain for his own selfish motives. It's got a very obvious Xenophobia Is Bad Aesop.
The Siamese Cats' "We are Siamese" from Lady and the Tramp is a bit of a special case, as the song itself is the characters' only appearance in the film. It still ends up being one of the most memorable scenes.
This Villain Song is unique in that there is no sound save McLeach's echoing voice and that the only image on screen is of him driving his gigantic truck into the desert. The scene ends within seconds.
"Yodel Adle Eedle Idle Oo!" might have been meant as a parody of the archetypical Villain Song, because it starts out in a typically "dark and sinister" manner, then evolves into a cheerful yodeling tune.
Instead of a musical number, Maleficent of Sleeping Beauty gets a Villain Poem, where she mockingly tells the "Sleeping Beauty" fairy tale to the imprisoned Prince Philip, gloating over her victory via Sarcasm Mode and Evil Laughter. It serves the same purpose as a villain song while being creepily low-key.
Near the beginning of The Aristocats, Edgar the butler can actually be heard singing "Rock A Bye, Baby" while pouring his mistress' sleeping pills into the cats' milk so that they will all fall asleep, therefore allowing him to kidnap them all and leave them all for dead in the French countryside. But then a pair of dogs attack him...
Actually, that was not to be the original song in the movie. There was originally intended to be another song in a different style, that got cut, called "The Pirate Song".
Mother Gothel in Tangled has Mother Knows Best, which takes on the tone of a demented version of Mary Poppins. This song doesn't gloat about an evil plan, it serves as musical exposition about how Gothel secures her acquired benefits (by subtly terrorizing Rapunzel into obedience). Then there's the reprise.
A song for King Candy, explaining how things worked in Sugar Rush, was deleted from Wreck-It Ralph as it didn't feel right for the story.
On repeat viewings, it can be fairly easy to view "Love is an Open Door" as a one-sided villain song. Anna is singing about how love conquers all. Hans is singing about how her naive belief in True Love will hand him the kingdom.
Cut from the movie, probebly replaced by "Love is an Open Door" is "You're you" - Also sung by Hans. In the same way as Open Door, it sounds sweet until his true intentions are revealed.
As Disney's Mary Poppins didn't have a clear villain, it would seem to be exempt from this rule, but "Fidelity Fiduciary Bank" gives it a try anyhow. Mr. Banks and his bosses at the bank are the closest thing Mary Poppins has to a villain until his Heel-Face Turn; he is against Mary Poppins herself, fun, and compassion because they interfere with order.
"Temper Temper", in the new stage adaptation, features the children's toys coming to life, growing larger than the children themselves, and holding the children trial for having lost their tempers — for, "children who lose their tempers lose everything else in the end!"
"Brimstone and Treacle", again from the new Mary Poppins, where the Banks' second nanny, Miss Andrews, explains her philosophy that brimstone and treacle with a good dose of tyranny is the best way to govern children. (Note that there is also a Dark Reprise in which Mary comes back, sets Miss Andrews' pet lark free from its cage and there is a showdown between two singing nannies which results in Miss Andrews having a taste of her very own brimstone and treacle as well as being forced into a giant birdcage and sent down below.)
"I'm Number One [You're Number Two]" in Muppets Most Wanted is a Villain Song Duet between Constantine (criminal mastermind and number one crook) and his associate, Dominic Badguy. It's not only celebrating their intention to pull off a series of heists and frame the Muppets, but Constantine reminding his flunky who's in charge.
In the Disney Channel original movie Girl vs. Monster, when the villainess, Deimata, possesses a supporting character and takes the stage from Skyler, she turns "Nothing's Gonna Stop Me" into a surprisingly rockin' villain song, ending with her seemingly forgetting that she's not in a musical and reaching into the camera. Unfortunately, we only get to hear a few parts of it.
Oddly, the lyrics of the main theme, "Fearless", don't seem to be able to decide if they're from the perspective of the hero or the villain. ("Iím stuck in your head / Iím back, back from the dead / Got you running and scared / I'm fearless...")
Fat Cat's "The Best Of Everything" from the Five-Episode Pilot "To The Rescue". Not to be outdone by "The Fat Cat Stomp", initially performed by Chip and Dale in drag in "Adventures In Squirrelsitting", but later reprised by Fat Cat himself in the next scene.
Irweena Allen ("Risky Beesness") has her own song, too ("You're The Best Bee For Me"), and Sewernose de Bergerac ("A Case of Stage Blight") joins the Pirates of Peejama performance. In fact, not even the Coo-Koo Cola jingle ("The Case of the Cola Cult") remains untouched by villains.
In the four-part TaleSpin pilot, Don Karnage reminds his Air Pirate underlings of what they do with "Sky Pirates".
The TV series for Disney's Hercules has Hades taking you for a tour of his taken-over city-state in "My Town".
"One Good Man" from "Song of Circe" also qualifies, as it's sung by Circe herself and shows her manipulative, deceitful personality very nicely. Also, it's sung by the wickedly talented Adele Dazeem...I mean, Idina Menzel.
Gideon from Gravity Falls gets "Widdle Ol' Me", a catchy gospel-inspired song, on his first appearance in "The Hand that Rocks the Mabel". It comes with just enough unsettling undertones to demonstrate he's a Villain with Good Publicity.
The Darkwing Duck episode "Paraducks" features an Elvis impersonator who does a number bragging about what a great thief he is. At the end of the episode Darkwing does his own heoric reprise about how no criminal is safe from him.
And then we get an awesome remix/ duet between Jack and Oogie from the game, seen here.
In fact, there's three remixes/duets of Oogie Boogie's Song in Oogie's Revenge, with the above being the final one. The other two are Oogie's Song and Casino Clash, plus a remix of Kidnap the Sandy Claws called Hail to Mr. Oogie.