Lampshaded by one of Anne Rice's vampire characters during a gathering of their kind. As he looks around at all the gorgeous males and females he wonders whether it's because vampires only choose to turn good looking people or if it's some aspect of vampirism itself that makes anyone who gets turned into one drop dead sexy in one way or another.
True Blood mostly averts it, but Eric and Bill are apparently walking sex gods.
Under the D&D rules, vampires gain a boost to Charisma, which measures among other things physical attractiveness and sex appeal, when transformed. This was parodied entertainingly in an early Antiheroes for Hire strip.
Doubly subverted by Carmilla in Castlevania: Lords of Shadow. The vampire queen prefers a woman's shape, but her deathly pallor and bloody red eyes place her easily into the Uncanny Valley. Her Absolute Cleavage comes off as more wanton than alluring, and her deep voice is harsh and commanding. Her true form amounts to a shaggy, hideous batlike thing that walks like a woman with flabby breasts...all in all, it's probably not a surprise that the heroic knight Gabriel is above her wiles.
Lampshaded and subverted by the Count himself in Fred Saberhagen's The Dracula Tapes, where he mocks van Helsing's fondness of the word 'voluptuous' and makes an offhand remark about having actually known some ugly female vampires and sympathizing with their plight. (He's also not above making a quip or two about his own looks, for that matter.)
With the exception of those based on the original Norse and Scottish mythologies, most "Dark Elves" in almost any Fantasy fiction. All of them. Especially the females. The Dark Eldar from Warhammer 40,000 are actually meant to be naked, but Games Workshop aren't permitted to sell nude figures to under-18s (a major part of their customer base), so they have just enough clothing to cover their naughty bits. Daemonettes of Slaanesh don't, though.
Even in stories that are based on Norse mythology, sometimes the Dark Elves are still depicted as drop-dead gorgeous. This◊ is the Marvel Universe version, for example.
Trinity Blood is a master at this. Talking to you, Cain Nightroad, Isaak Fernand von Kämpfer and Dietrich von Lohengrin. Radu Barvon could also count.
Speed Grapher rather enjoys playing this trope as straight as possible, then immediately deconstructing the idea as brutally and horrifically as possible.
Dio Brando, from JoJo's Bizarre Adventure, elevates this trope to practically a superpower. Many of his subordinates follow him just because of his charisma and beauty. Many of them (of both genders) outright wanna jump his bones, and some succeed (Vanilla Ice and Enrico Pucci). To be slightly fair however, he was already extremely attractive BEFORE he became completely evil, and its implied that he is using his Stand Power to aid him in this. Dio's beauty is so amazingly mythical leveled that it even seduced a blind man.
In D.Gray-Man most of the Noah that exemplify this trope, specifically Tyki Mikk (Pleasure of Noah) and Lulu Bell (Form of Noah). Oddly averted in their comically round but nonetheless badass leader, The Millennium Earl, but as of chapter 187 he plays this straight with his human form.
In later chapters, evil Allen.
Take one look at Pretty Sammy and her antagonist, Pixy Misa, and tell me which is the evil one. It's even worse in the alternate universe spin-off Sasami Magical Girls Club, as when she's possessed by evil Misao goes from being a 10-year-old girl to a voluptuous 20-something with very little clothing.
Most directly played in the 2nd season. Chibiusa is a typical 6-year-old girl (physically anyway). When Death Phantom captures her and brainwashes her into the evil Black Lady, she becomes a well-endowed woman in her 20s.
Similar remarks apply to Hotaru's transformation into Mistress 9 in the third season.
Force continues the tradition with Arnage of Huckebein, an Evil Redhead with bared midriff, nice rack and hotpants, as well as her teammate Curren who wears a fancy sports bra thing she fills out well along with shorts.
Johan Anderson plays up the White Hair, Black Heart trope in the outfit he got while possessed by Yubel — sleeveless trenchcoat, baggy jeans, and leather straps everywhere, all in a fashionable shade of dark slate blue-gray.
Camula is one of the only women who can be evil, sexy, and play cards at the same time. (And she was one of the few villains in the franchise that proved incapable of redemption, which for Yu-Gi-Oh, was rare.)
Played straight in Yu-Gi-Oh! with Kaiba, Pegasus, Yami Bakura, and normal Marik. Completely averted, however, with Yami Marik, who is prone to having veins randomly pop up on his face, usually while his eyes are out of proportion and his tongue sticking out.
In Princess Tutu, Rue demonstrates a classic case of this: when she transforms into her evil alter ego Princess Kraehe, her previously fairly standard ballet costume is now something strapless, backless, and cut down to her bellybutton in front.
Also, once Mytho is infected by the Raven's blood in season 2, he becomes much much more sexually assertive. He flirts openly, tracing his fingers over girl's hearts, draping his arms around one woman's shoulders, and essentially coming on to every girl he meets in an attempt to take their heart from them as a sacrifice. Although towards the end of the series, when it takes him over more and more, he becomes less sexy and more squicky.
In Monster, Johan Liebert is by far the most attractive man in the entire series. He is also, without a shadow of a doubt, the most evil.
Dakki, the Big Bad of Houshin Engi. She's well-formed, and often wears revealing outfits. Her magic weapon even gets a power boost when she strikes sexy poses.
To a mild extent in an early episode of the Rockman.EXE anime, where the baddies temporarily turn Roll evil - while her outfit doesn't change, she gets a whip and a dominatrix personality for the duration of this effect.
Pretty Cure rarely takes this approach, with the female characters generally balancing out the positive aspects of their looks with things like odd-looking eyes, conspicuously odd skin tones, and so on. Eas, though◊...
Doesn't stop there; feast your eyes on CirucciThunderwitch: Busty chest, curvy figure, attractive voice (when she's speaking calmly), and whip-toting, with a dominating personality.
Ulquiorra Cifer has a well-built body and a nice, deep (moreso in Japan), mildly alluring but rather sexy voice.
Aion from Chrono Crusade plays with this, particularly in the anime adaptation, where he goes from being attractive and charismatic to willing to sleep with Anything That Moves. However, this trope is also used in the anime to make him creepy and squicky — he not only happily seduces those that are willing to sleep with them, but is implied to attempt to rape many of the ones that aren't willing (and may have even succeeded in one case).
Though more case of nuts and misunderstood, GUN×SWORD features ex-prostitute Fasalina, who is still gratuitous enough to reveal some of her ample bosom (though not so Stripperiffic), fights on a strip pole, long gorgeous hair... Guess which side she's on.
Light Yagami from Death Note is much hotter when evil than when innocent.
Misa Amane, Teru Mikami, Kiyomi Takada and Mello also qualify.
Governor General Godel of Mahou Sensei Negima! is arrogant, manipulative, underhanded, and undeniably evil from the first time we see him. He also has a stylish suit and glasses and is very hot even while tormenting Negi.
Slan and Griffith are pretty hot, especially considering what most of Berserk's demons look like.
Meanwhile, the ladies get Beelzemon, who's very blonde, has a husky voice, and wears spiky armor, tight leather pants, and a very clingy shirt that may as well have been spray-painted onto his very defined abs. The "evil" part is subverted, however.
Alucard from Hellsing. It's difficult to be more evil than someone who essentially orgasms from ripping people into pieces and has consumed approximately four million souls over his centuries of existence, and it is just as difficult to be sexier. As someone on this very wiki notes:
Medusa and Arachne from Soul Eater (ever better, Medusa when she possesses Arachne's body). Also, Asura when he appears more "pretty boy" than Eldritch Abomination. Mosquito, when in the form he uses to slice Kid's arm off. Free, who seems to get bigger, taller, and brawnier with every chapter he appears. In some cases Crona and Ragnarok before becoming good.
Magneto. The chiseled, aristocratic features, the silver hair, the tragic past... he's thrice her age and still makes Rogue weak in the knees. (They married, had kids, one named after Charles Xavier himself, and were insanely happy in an Alternate Universe, to the displeasure of the Gambit of the main universe.)
Mystique. Given she's a shapeshifter it is almost certainly deliberate.
The Hellfire Club evoked this trope in their earliest appearances, with the White Queen, Tessa and both Black Queens wearing leather fetish gear. The gentlemen of the club were of varying degrees of attractiveness, but they did manage to be well-dressed at all times.
Speaking of Sue Richards, when she was possessed by Malice, an evil mutant, she clearly fit this trope, and how!◊ The aspect of her personality remained with her and popped back up again years later, resulting in her Darker and Edgier outlook when she became more of an Action Girl.
Poison Ivy's an insane, plant-obsessed eco-terrorist whose only human friend is The Joker's on-again, off-again love interest and partner-in-crime. Her interests include eliminating humanity to make the world safe for plants and poisoning people by kissing them. She was modeled on Bettie Page, generally appears clad only in something skintight and a lot of leaves, and is even tempting enough for Batman.
Batman: Why are all the gorgeous ones homicidal psychopaths? (Batman & Robin)
Catwomanhas been rendered more sympathetic as a character over the years, but she's a Spy Catsuit-clad whip-toting villainess who's not above killing when she has to. Like Ivy, she too proves attractive for the Dark Knight, sufficiently so that someone seeking to break Batman hired an actress to dress up as Catwoman and seduce him.
Harley Quinn: Former Arkham Asylum psychiatrist who falls head over heels for The Joker and reinvents herself as a catsuit clad, female version of him. Happy to murder henchmen at the drop of a hat and always drawn in a painted-on harlequin jester's outfit that frequently gets 'upgraded' to a latex version.
White Rabbit, whose costume is basically a lingerie.
Ava Lord, stereotypical vamp/Femme Fatale from Sin City story "A Dame to Kill For" is most sexy when posing next to her dead husband whose death she caused, all the while faking stories of the guilty of her crimes on the phone and smiling all the way.
Blue Eyes and Mariah, the Colonel's assassins. Blue Eyes' speciality is Death by Sex, even.
ElfQuest has Winnowill, who is incredibly hot and just gets more and more deadly. Also the warlord Grohmul Djun, who's a massive hunk, and Door in the "Forevergreen" arc, who's a psychotic pretty boy.
One half of the modus operandi of Moonstone/Karla Sofen of the Masters of Evil and the Thunderbolts. The other half is being a complete psychopath. She was all over this when she became the "new" Ms. Marvel.
* This was even lampshaded in the comic when Nightmarity says at one point, "I'm so hot, I should be on fire!"
Overlord, who appears in Transformers: Last Stand of the Wreckers and Transformers: More than Meets the Eye, is just about this personified, with his handsome (for a giant robot) looks and campy, charismatic, and theatrical mannerisms. In fact, one defining trait of Overlord has been his luscious lips. Possibly lampshaded by IDW themselves with the alternate cover for issue 15 which is basically a close-up of Overlord's lips.
Unlike the films, Loki inverts this in the comics. Originally Loki's attractiveness varied from artist-to-artists, with some drawing him as a scarred, ugly old man. However, in recent comics Loki was reborn as a child, who then got possessed by his old, evil-self's memory, and now aged up. Now, he's had a Heel-Face Turn and became dashingly handsome, as well as now openly bisexual, with all the allure that brings. Fans approve, to say the least.
In The Return Alexia and Akumi clearly believe Evil should be Sexy, but they both take it to such extremes they end up as a Fashion-Victim Villain and are soundly mocked by the heroes about their dress sense. The trope is played somewhat straight in that anyone converted into a succubus becomes a Perky Goth, but this is immediately subverted in that they are not Always Chaotic Evil and are free to choose whether they are good, evil, or indifferent.
Queen Of All Oni: Right, one of Jade's Shadowkhan bodyguards/enforcers, is described as being "oddly handsome" once he takes his mask off. Presumably, this applies to his twin Left as well.
In the Hunger Games fanfiction Some Semblance of Meaning, the girl from District One, Amber, plays up the "alluring" angle in her interview, is very attractive and flirtatious, and also happens to be one of the most depraved tributes.
Films — Animation
Sinbad: Legend of the Seven Seas featured a particularly potent example in the villainess Eris, goddess of Chaos. She had the evilness of Ursula, and the good looks of Megara rolled up into one evil, but compellingly seductive package, a character who's both manipulative and unapologetically sexy.
Sleeping Beauty: Maleficent is an unconventional but considerably notable case of this, especially in scenes earlier in the movie. See for yourself. She might not have a noticeable rack or rear, but her feminine looks, graceful style, and seductive voice (provided by Eleanor Audley) combine to create a sense of macabre beauty to her, which really sets her apart from most other major female Disney villains, at least ones known up to that point. (Whom, for whatever reason, tended be portrayed as unattractive.) An interesting application of this occurs in that Maleficent will be played by Angelina Jolie in the live-action prequel Maleficent.
Done quite bizarrely at the end of "Let It Go", where Elsa does a Sexy Walk and then bedroom eyes straight at the camera, which coupled with her off the shoulder ice gown with a slit up to her knee makes her seem like a sexy sorceress. Except she doesn't act anything like this anywhere else in the film, making the whole thing a Big Lipped Alligator Moment.
Prince Hans is a much straighter example, deliberately invoking the Prince Charming trope to hide his true nature, and keeping up the act even after leaving Anna to die..
Anne: Oh! You gotta believe in God! But I don't believe that God created Man in His image. 'Cause most of the s—t that happens is because of men. Naw, I think men was made in the Devil's image, and women were created outta God. 'Cause, after all, women can have babies, which is kinda like creating. And which also accounts for the fact that women are so attracted to men. 'Cause let's face it, the Devil is a helluva lot more interesting. I've slept with some saints in my day, and believe me, I know what I'm talking about. Egh-boy! So, the whole point of life, the whole point of life, I think, is for men and women to get married so that God and the Devil can get together — and work it out. Not that we have to get married or anything. God forbid.
Dracula is often portrayed as having a magnetic, sexualized presence, fueled by the erotic overtones in the original book. In Ed Wood, Bela Lugosi says he turned down the role of Frankenstein's monster because it wasn't sexy, like Dracula.
End of Days: the real threat of Satan is that the female protagonist finds him so damn sexy.
Many of the villains in the James Bond series are sexy women. Notable examples include:
Fiona Volpe, SPECTRE's "Execution Branch" in Thunderball.
Subverted in Spider-Man 3. When Peter Parker flirts with The Dark Side due to the symbiote costume, he acts more sexually assertive and seems to think he's suddenly the hot stuff. To the objective gaze and the befuddled look a random girl gives him in the street, he just now looks like a more sleazy dork. He's still fundamentally himself, after all, as no matter how self-confident and sexually assertive he's acting, he remains a nerd and has no idea how to carry himself otherwise. Furthermore, in a neat little bit of irony that underscores this point, the only women who he does manage to charm with his new assertive manner were already attracted to Peter when he was "good" anyway.
Christian Coulson as the diary image of Tom Riddle, to some degree.
Helena BonhamCarter as BellatrixLestrange. Bellatrix may very well be a Death Eater and a murderous sadist who's prepared to kill her own niece over who she married, but she's still portrayed as seductive and attractive, even just after fourteen years in wizard prison.
For the brief time that he doesn't look like Mad-Eye Moody, Barty Crouch Jr is played by a deliciously twitchy David Tennant.
Prince Septimus from Stardust. Also, Lamia starts out as an old crone but becomes young and sexy due to digesting the remains of a star's heart. Subverted in that each time she uses magic, she regresses more and more back to her previous, hideous state.
In The Devils Advocate, Satan is played by Al Pacino as a powerful attorney with a forceful, magnetic personality that seems to drive women wild. Connie Nielsen plays his daughter, who tries to tempt Keanu Reeves to the dark side with her super sexiness.
The X-Men series give us Mystique; a female mutant who's a) on the bad guys side, b) perpetually naked since those clothes aren't really clothes, and c) very flexible.
Basic Instinct and Basic Instinct 2. Catherine Trammell is a dangerous, manipulative, sociopathic nymphomaniac and compulsive multiple murderer, but still portrayed as a sexy woman who can charm both men and women into her bed.
Many Hammer Horrors, especially ones directed by Terence Fisher, not only have evil as sexy but evil as overtly sexual— though this was always a popular subtext in vampire stories.
A Discussed Trope in The Courtship of Eddie's Father, where the son tells his father that bad women can be identified in comic books by skinny eyes and big busts.
John Waters' Female Trouble subverts this. Donna and Donald Dasher discover Dawn Davenport (a 300-pound juvenile delinquent turned career criminal) and get her to work as a model to prove that "crime is beauty". Dawn endured such things as acid being thrown on her face by her ex-husband's lesbian aunt while the Dashers kept saying that the gravity of her crimes was making her more beautiful than ever before.
When Sam Rockwell's character does his Face-Heel Turn in the first Charlie's Angels film, he gets a stylish Evil Costume Switch and reveals himself to be far more hip and self-confident than he had previously let on. He's also got a super-sexy girlfriend.
Jackson Rippner from Red Eye. He's a bad, bad man but he has buckets of charm.
Col. Tavington is supposed to be the ultimate Evil Brit. Being played by Jason Issacs (aka Lucius Malfoy) makes it kinda hard to root against him (though he does ultimately manage it.)
Candyman is pretty hot. He has that awesome voice, and he's so handsome and tall. While he mercilessly hacks everyone else to death, his pursuit of the heroine is overtly seductive.
From Dusk Till Dawn: Santanica Pandaemonium, played by Salma Hayek. First appearance in the film? Performing a slinky dance whilst dressed only in a bikini and a boa constrictor. She indulges in a lot of stroking people with her feet during this, as well.
Oddly enough, Halloween's Michael Myers is meant to be this. According to Word of God, Tony Moran's "angelic" face is exactly why he was hired to play Myers in the brief unmasking scene of the first film. And the scar on Michael's eye wasn't supposed to be as ugly as it turned out to be, but prosthetics got a bit carried away when applying it to the actor's face.
Mini of Mini's First Time is a very sexy seductress, and she is also evil to the core.
In Tolstoy's Anna Karenina, the hero is arguably an aristocrat named Kostya Levin. He is a rich handsome nobleman who spends all his time thinking of how he can best use his riches to benefit poor people and humanity in general. Amazingly, this hunky millionaire has trouble attracting women. Meanwhile, Anna Karenina, while not perhaps evil — she doesn't go out of her way to be bitchy — is selfish and ruins everyone's life. Men are drawn to her as moths to fire. Probably not one in ten thousand people have ever heard of Kostya. But every literate person in the world has heard of Anna Karenina.
William Sleator's Strange Attractors features this rather prominently. A boring scientist and his plain daughter have evil duplicates, which are nearly identical, just evil and slightly older. They're presented as incredibly sexy and interesting, to the point that the protagonist rebuilds a device which may destroy all time just to be with them.
Villains in Mercedes Lackey's Heralds of Valdemar books are frequently mages who gratuitously make use of magic to make themselves ridiculously attractive, to the point where the nastiness of a particular character can be discerned from how attractive the main character finds them. That is, physically attractive. Those sorts of mages hardly ever get (voluntary) dates.
Similarly, sorceresses in The Witcher are chosen by being gifted in magic. Since noble families are the ones most sorceresses come from and would better benefit the family to be married off to other nobles ASAP, the only ones sent to receive training in magic are ones who are somewhat lacking in the looks department. And one of the first things they learn is modifying their own body. Not all sorceresses are evil, but most of them sure as hell are bitter.
Lanfear of The Wheel of Time is a singularly attractive and alluring woman, supposedly one of if not the most beautiful in history, who makes all the male leads drool and the female leads envy. She's also reputed to be the most powerful female dark mage in the world. She's in good company; her fellow Forsaken aren't too harsh on the eyes either. Graendal's a voluptuous temptress whose perverse kinks are the stuff of legend, Rahvin's a dashing ladies' man, and all the rest scrub up pretty well except Aginor and Balthamel and Balthamel is eventually placed in the body of a beautiful young woman and assumes the persona of a brazen (but seemingly harmless) hussy. Most female Darkfriends are hotties, most of the Black Ajah are (at the very least) imperious and regal, both aspects of Slayer are attractive (since they're both said to strongly resemble their good looking relatives), and all the biggest Knight Templar jerks in the Children of Light are exemplars of rugged aryan manhood. Then again, there just aren't many ugly people in The Wheel of Time, period.
Interestingly in Slayer's case, he's Lan's uncle. Lan isn't known for his beauty, but his good (well manly, rugged and so on) looks. In "A Crown of Swords," Nisao Sedai states that "women have been chasing Lan since he was a beardless boy...He was quite a beautiful boy, however hard that might be to believe now."
The Stainless Steel Rat: Crook turned galactic agent 'Slippery Jim' diGriz falls for the villainess he's pursuing not just because she's beautiful, but because he genuinely admires her brilliant criminal mind. If only he could get past the fact that she's a sociopathic killer...
Angelina used to be extremely ugly in her youth and used the crime money for drastic plastic surgery to gain super model looks (cosmetic surgery is even better in the future). diGriz only met her after she was beautiful. How much insults from others about her ugliness led to her life of evil is a good question. While he did fall in love with her while she was evil, he then brought her to justice so she could be "cured" of her evil (psychological) thanks to some future Applied Phlebotinum. After the cure she no longer approves of killing, although she enjoys robbing (non violently and only the rich) with her husband (in between their constant saving of the galaxy).
The Dresden Files plays this one straight and subverts it with vampires: White court vampires are made supernaturally sexy by their inner demon - Lara Raith is described as so beautiful that it's hard to describe her actual features as they are obscured by her beauty (hence her success as a porn star), Thomas Raith is described as "The Forgotten Greek God of Body Cologne," and his very evil father is described in much the same terms. The Red Court subvert it: On the outside, they look beautiful, but under their flesh-masks they are hideous, slimy bat-things. The Black Court, on the other hand, avert this trope entirely; they are desiccated corpses, complete with dried eyeballs, missing limbs and rotting hair.
Mention should probably be made of the Fairy Queens, too. Though they are less evil and more on a different scale of morality altogether, the fae that care to look human at all tend to look like very attractive ones, and many are effectively minor gods of fertility or nature with all the sensuality and virility that implies.
Andrea, from The ZoneWorld War III novels by James Rouch, uses her incredible beauty and sociopathic skills of manipulation to get the other male soldiers to teach her new means of killing. Major Revell, the commanding officer of the unit, is obsessed with her, even though he knows full well she's a crazed killer.
The Picture of Dorian Gray by Oscar Wilde, in which the protagonist's wrongdoing causes his portrait to age and become ugly, while he remains young and beautiful. Until the end, that is.
The White Witch from The Chronicles of Narnia is described as being the most beautiful woman ever by many men in the books, despite having brought about the complete depopulation of her home world and a hundred years of perpetual winter to Narnia.
In Kire are the hulders really beautiful pretty much like the White Witch from Narnia above, and could be covered in blood but still be found attractive, they can make friends fight over them just for fun, but apparently this doesn't work on women. Although it's really ambiguous wherever they're really evil or not. But somehow is the hulder that Erik's mother killed still alive and still wants to take Kire with her...
Tom Riddle was originally very attractive, and used his looks to his advantage. However, even before his resurrection, experiments with dark magic ruined his looks to the extent that people can't even recognize him anymore.
Bellatrix Lestrange also used to be attractive, before she went to Azkaban. After breaking out she still retains some of her looks, which is saying something, because spending years around Dementors is not good for your looks.
Then there's Grindelwald when he was young. J. K. Rowling makes sure everyone gets a good description, even the dark lords.
The Sword of Truth series had the Mord-Sith, a cadre of gorgeous, leather-clad women... whom the Big Bad had psychologically broken and uses to torture his enemies. When he is deposed, they become Dark Is Not Evil retainers to the heroes.
The Stand: Possibly. It can be said that Randall Flagg is an example of this trope, in his control of Nadine. She would have gone to the good side in Boulder, she says, were she not madly lusting after Flagg. Nadine can also be an example, in that it is difficult for men to resist her, and she uses sex to keep Harold evil.
The Belgariad gave us Queen Salmissra of Nyissa. Well, the most recent Queen of Nyissa to bear the name, at any rate. Swathed in a diaphonous gown and jewelry reminiscent of a belly-dancer's outfit and portrayed as highly sexually active as well as being prepared to sell Belgarion out to Torak.
Laharl’s aunt Yasurl from the Disgaea Novels. She is evil to the bone and abused Laharl then he was in her care, this affected him so much that he has had vile allergic reactions to sexy women ever since.
Toyed with in Animorphs in the person of Taylor, a deeply disturbed girl who allowed a Sociopathic Soldier of a Yeerk to take over her mind in exchange for a new face. She's described as being very attractive in the physical sense, but is so artificial and emotionally screwed up that no one cares. Pointed out by Tobias when he morphs Taylor and receives far more positive male attention than the real thing:
"We were mirror images, literal carbon copies. But I was alive. Taylor wasn't. Not really. I had a sense of humour. Taylor had a coldness that enclosed her like a shield. The kid could see this. Anybody could."
Damien the Demon King in the Iron Witch trilogy is described as being very, very sexy to the point that every little thing he does makes Donna swoon and she has to keep reminding herself that they're enemies just so she can talk.
Star Wars: Fate of the Jedi has a planet full of Sith who play this straight (being obsessed with beauty), and especially the Keshiri natives.
While it's a very mild example, in the Stargate Atlantis episode "This Mortal Coil", "Dr Keller" is revealed to be a Replicator. Once this is revealed, "her" jacket is unzipped. No cleavage or anything, but someone's invoking something...
Invoked by the Goa'uld, who as vain, egotistical Evil Overlords deliberately take the best bodies they can find. A former host said that beauty is considered a curse on her world because of this. Though how a slimy body-controlling snake would know what humans find attractive is anyone's guess.
Adria in season 10. As Vala (her mother) put it "Origin is about to become much more appealing to the males of this galaxy."
Not especially "evil" but Blackadder got a lot sexier once he became a total bastard. The flattering clothes, a nicer haircut and the amount of the leather he wore in series II might have had something to do with it.
The Master from Doctor Who was designed to be sophisticated, handsome and charming (most of the time, at least), particularly to contrast against the Doctor's more... esoteric appearance. Ainley's incarnation slipped between this and Ax-Crazy, and while Simm's incarnation was almost entirely Ax-Crazy there is still the mountains of Fetish Fuel that's dumped on him in "The End Of Time."
The Rani wasn't all that bad looking herself, getting a stint in one serial as The Baroness.
There's a reason why the Supernatural fandom loves "Skin", "Devil's Trap", "Born Under a Bad Sign" and "Dream a Little Dream of Me" so much. It's because Evil!Sam/Dean/John ooze sexual appeal (even more so than when they're being good) and also because they seem to touch each other a hell of a lot more.
Most of the population of the Mirror Universe in Star Trek. Turned Up to Eleven for the Mirror Universe version of Kira; a catsuit-clad Depraved Bisexual version of a character who's normally portrayed as being extremely moral.
Sheriff Buck of American Gothic falls under this trope, and his schoolteacher girlfriend Selena Coombs embodies it.
Adam Monroe. Evil Brit for a sexy foreign accent. And, be it in armour or in that suit with the shirt opened a significant way down, he's a snappy dresser. Nevertheless, he suffers from delusions of grandeur and believes that culling the human population with plagues is a good idea.
The show was clearly TRYING for this with Evil! Future Claire in season 3. Unfortunately, their ideas for sexing up Claire were limited to an all-black wardrobe, a different hairstyle, and a TON of lip gloss.
And then there's Samuel. Maybe it was the fact that he's played by the same actor who played Magnificent BastardT-Bag, or maybe it's the accent, or the charisma, but he is just sexy. The eyeliner and the Badass Longcoat just add to it.
Angelus, Spike, Darla and Drusilla, who back in the day were the sexiest and most murderous group of vampires in history.
Faith is the Evil Counterpart to Buffy and - since Evil is Sexy - she wears skimpier clothes and is unabashedly promiscuous and seductive. In season 4, Willow lampshadingly describes Faith as a "cleavagey slut-bomb walking around going, 'Oh, check me out, I'm wicked cool, I'm 5 by 5.' "
Lilah Morgan really works this trope, especially in Angel season four, during her relationship with Wesley.
Glory, a.k.a Glorificus. She wants to destroy the world, but that doesn't keep her from being pleasurable to look at!
Lindsey may be an at-best-morally-ambiguous corrupt lawyer, but he is also incredibly pretty.
Evil liaison, Child of the Senior Partners, and Lindsey's main squeeze Eve is pretty hot too.
Prince Dirk Blackpool (played by the luscious Duncan Regeher) the black leather clad villain of Wizards And Warriors.
While the heroic Taja wears reasonable clothing, all the villainous females of Mortal Kombat: Conquest wear revealing outfits—Omegis to the point of wearing nearly nothing. The well-built Shang Tsung usually wears a vest over his muscular body, but spends a lot of time with his shirt off.
Power Rangers had some valiant efforts in Scorpina and Divatox, but with Astronema, it really took hold, as she had a liking for black leather and changed her hair style and color every five episodes or so (if you're watching episodes out of order, it's a great way to check where you are in the plot). Made more evident because Astronema was actually The Hero's amnesiac sister. When she reverted to the nice and pure Karone, she had straight blonde hair and modest clothes. When brainwashed to become Astronema again... form fitting black leather and cropped red hair. When Karone returned in Lost Galaxy as the Pink Ranger, she evoked this by dressing up as Astronema to get back the Pink Ranger's Quasar Saber, but was still shown to wear black leather in her civilian form.
From The BBCRobin Hood we get Guy of Gisbourne and his sister Isabella. Izzy is initially introduced as an ally to Robin, but as soon as she throws in her lot with the bad guys her outfits (which were always designed to make her Ms. Fanservice) also become leather. On the same show, when Allan-a-Dale turns traitor, he gets an Evil Costume Switch (the sheriff actually says "upgrade this boy to leather").
Wilhelmina Slater from Ugly Betty. Fair enough, she's played by Vanessa Williams, who was Miss America, but there's a certain lustful nature about her being evil.
Ronnie Gardocki from The Shield, supplying a helping of facial hair Fetish Fuel with the character's mustache and an evil Nerds Are Sexy vibe that helped him stand out from the rest of the Strike Team.
On the other side, there is Curtis "Lem" Lemansky, who was a walking poster for Mr. Fanservice with his sleeveless shirts and muscular form.
While there are plenty of ugly baddies in Farscape, a fair few fit the mold, especially Crais, Grayza, and Scorpius (for the kinky among us). Grayza unabashedly uses her sex appeal (and self-created Love Potion) to her advantage.
While not evil per se, Celia Hodes on Weeds does somehow manage to make being an insufferable cunt oddly sexy.
Done in a rather Squicky way in an episode of Nostradamus Effect involving The End of the World as We Know It and some Book of Revelations quotations, where the Anti-Christ and the False Prophet is portrayed by particularly good-looking actors-and that's not counting the manifestations of the Seven Seals. All of them are dressed in suits, for some reason.
Polly Walker as Atia of the Julii in Rome, partly for being evil, and partly for being a total bitch.
Normally, Hal from Being Human is a very repressed, anti-social vampire on the reform. When he falls off the wagon, though, or when there is a flashback to his bloodier days, he instantly becomes charming, charismatic, and (frequently) less clothed.
Once Upon a Time loves this trope. The most prominent examples being Regina, whose neck line is always lower when she's the Evil Queen, and the drop dead gorgeous Captain Hook on the male side of things.
Fergie's psychopath stripper character in the music video for "Beautiful Dangerous", with Slash. Not only does she succeed in drugging him, tying him to a bed, and all that junk, but also kills him at the end with her knife!
Loki actually subverts it, if you go over the stories in chronological order and ignore the aspects tossed in by Christian translations. In the earlier stories he swung between Magnificent Bastard, Sociopathic Hero, and Trickster Archetype depending on which story, but also took the role of Butt Monkey even more and often found himself victim to Disproportionate Retribution (like the time his mouth got stitched closed and cut open again with a pocket knife (resulting in a Glasgow Grin) because he lost a bet and couldn't pay up, and before that, in the same story, nearly getting his head cut off for shaving off Sif's hair), even if he personally didn't do anything wrong (like being raped and impregnated by a horse because he agreed to letting a builder use said horse to help him build a wall). By the time he actually had the Face-Heel Turn that lead to him becoming the stand-in for Satan in modern stories, the punishments had built up and by that point, his face would have been horribly scarred by the afore-mentioned Glasgow Grin and having venom dripped into his eyes. The times when he was handsome were actually the times he was a good guy.
Bally's Mata Hari pinball, which depicts the title character as a seductress and German spy.
Fierna, the nominal ruler of the fourth layer. She's an embodiment of Lust, after all.
Maybe mariliths too, if you're into that sort of thing. They're demons that have the upper bodies of beautiful women (with six arms), are usually scantily dressed (at best) and serpentine lower bodies. Of course, they usually have swords in each of their six arms and will probably try to kill you before trying to tempt you. (If one does try to tempt you, trust me, it would likely be a Fate Worse than Death.)
Slaanesh in Warhammer and Warhammer 40,000 has this reputation, being the God of Evil representing sensations in all its forms. Unfortunately while a cultist might start out as this, their senses are quickly burned out by so much excess that they have to go to even greater extremes to feel anything at all, to the point that eyes for nipples seem a reasonable option. They take every potential kink, then take them beyond sanity, morality, or anything someone in their right minds would find appealing.
On the other hand, one of Slaanesh's many "gifts" make its followers appear sexy or lovable to others, so much so that it can cause an enemy to fall in love with them and refuse to harm them, become so attracted to them that they won't run away even when they're being massacred, and force them to go wherever the psyker wants, even through minefields.
The Dark Eldar of 40K wear either skin-tight leather or barely anything at all, especially for Lelith Hesperax and the entire Wych sect, and are theFetish Fuel faction. This makes sense given that their ancestors created Slaanesh by essentially orgying so hard they tore open a hole in reality. The original Warhammer Dark Elves play this trope much straighter; there seems to be a correlation between how powerful a Sorceress is and how much skin she shows. And the Death Hags look about as far from the usual use of the word 'hag' as it is possible to get.
The Vampire Counts have their own version of this, and the original vampire bloodline is entirely composed of this in the "present day". Lahmian vampires are specifically known to use their seduction to enslave entire populations rather than using outright force, and all Lahmian vampires are female.
The AbyssalExalted have a choice: as they get more powerful, they either become decayed and corpselike, or deathly but alluring.
There's a bit of this in the Infernal Exalted too, given that of the five signature characters, one's a White Hair, Black Heart type and one's a freaking bondage nun. Oh, and Manosque Cyan, who's hard to describe in these terms but is damn good-looking anyway.
Tales of Symphonia: Zelos makes a career out of being a Lovable Sex Maniac, and he's the other party member guaranteed to betray you. In this case it's up to the player to decide whether it's a subversion, because Zelos can redeem himself and rejoin your party, or you can be forced to kill him.
Tales of Vesperia has the suave, clean-cut, well-spoken Schwann compared to the Dirty Old Man/Loveable Sex Maniac that is Raven. Just listen to how he addresses Judith during the boss battle, for one. On the more "Morally Ambiguous is Sexy" side, compare fully-armored Flynn with Yuri, who shows quite a bit more skin and occasionally hits on the girls in his party for the lulz.
Deus Machina Demonbane takes over half the stuff from the Cthulhu Mythos and gives it this treatment if it was a canonical asshole (or at least antagonistic to humanity to begin with) in the source. That said, the queen of this trope is Nya(ralathotep). It's hard not to find the Crawling Chaos hot when it appears in the form of a Hot Librarian with Absolute Cleavage who can also be a Futanari and Bi the Way. For bonus points, she has some creepy sexy going on during her most dickish moments.
Any of the (humanoid) villains whose faces you can see. The Emperor, Sephiroth, and Ultimecia (in addition to the above characters listed) are deliciously sexy. On the other hand, there's Jecht and Gabranth.
In Birth by SleepVentus, who was a bit scrawny, gains muscles and a sexy bodysuit the moment Vanitas took over his heart.
I-No from Guilty Gear. Red leather? Check. Nice body? Check. Shows it off at every opportunity? Check. Has a voice set jam-packed with innuendo and double entendres? Check. Witnessed the slaughter of a village for fun in one of the Drama CDs? Check. Wants to torture Dizzy by tearing her wings off and cooking them? Check.
Sonia, one of the main antagonists in Fire Emblem 7, wears nothing but a black corset, an elongated loincloth thing that goes to her knees, and stiletto heels. Oddly enough, she's not very popular, probably due to her tendency to Kick the Dog. The dog being her own (adopted) daughter.
Also Limstella, Nergals most powerful creation, who is even hotter then Sonia. Only she doesn't act very "Evil" because she's emotionless.
La Pucelle plays with this a bit. When a character turns out to have a Superpowered Evil Side, it manifests at night, implying that she's going out in her sleepwear... which just happens to be some rather sexy-looking lingerie.
Millenia from Grandia II. She's not evil (she is a party member, after all), and not exactly heroic (she isan aspect of an Evil Overlord, after all), but man, is she hot or what?
Young Ocelot in Metal Gear Solid 3. Volgin, on the other hand, averts this trope with extreme prejudice.
If you fail to save Richter's girlfriend Annette in Castlevania: The Dracula X Chronicles, she gets turned into a vampire who wears incredibly revealing clothing. Succubi and other Cute Monster Girls abound in this series, especially the Sorrow games.
Portal. The subtitles explicitly state that GLaDOS' voice becomes "more seductive" during the final battle, and has that setting on for the majority of Portal 2.
StarCraft: Kerrigan becomes much sexier when she stops caring about what anyone thinks, slaughters people for fun, and coincidentally takes on the appearance of a mean naked succubus.
While, with some specific ugly examples, most characters in Koei's Warriors games series (Dynasty Warriors, Samurai Warriors, Warriors Orochi) are good looking, those considered evil (or at least morally dubious, given the series mostly Grey and Gray Morality) can be absolutely GORGEOUS. Here's some examples:
Cao Cao, the most elegant of the Three Kingdoms' rulers, and a perfect example of a Magnificent Bastard.
Cao Pi, Cao Cao's son. Handsome, dashing, cruel and ambitious.
Zhen Ji, Cao Pi's wife (what IS it with this family?), probably the hottest lady in the Dynasty Warriors series and a bitch.
Sima Yi, Cao Cao's arrogant advisor. One of those elegant, almost feminine villains, although he isn't flamboyant at all.
Zhang He, however, IS flamboyant.
Diao Chan, a sort of Chinese Helen Of Troy. So many men died or killed for her, she can't possibly be pitied.
Lu Bu, considered the most monstrous warrior of ALL the Warriors series, is the manliest, most gorgeous guy you could imagine.
Nobunaga Oda, considered to be the baddest of Samurai Warriors' characters (and indeed, portrayed constantly as a villain in fiction) is an elegant, charismatic villain.
No, Nobunaga's wife, actually gives Zhen Ji a run for her money in the sexiness department, and she has the Femme Fatale role down to a T.
Kotaro Fuma. Sexy, in a VERY villainous, fetishy kind of way.
Kojiro Sasaki, Musashi's rival. Another one of those feminine villains.
Date Masamune, who was turned into a villain in the Warriors Orochi franchise. He's so damn ruthless and arrogant, the most aggressive, and most Bishōnen amongst the men (not women) who side with the Tokugawa in Sekigahara.
Orochi The Serpent King. Can give Sephiroth a run for his money in the "I'm gorgeous and evil, and you love me for it" department.
Unless you romance her in Throne of Bhaal.. then you can make her True Neutral.
Resident Evil has Excella Gionne for the guys and Albert Wesker for everyone. Also Alexia Ashford has a killer body in her human and first form (in this she is actually naked!) but her breasts actually get BIGGER when she transforms into her 2nd and third forms.
The young James Marcus seems to have been invented for the sole purpose of adding more bishonen to the series.
The portrait of the female Necromancer in Battle for Wesnoth 1.6 is drawn in this way (the posing and all), despite the fact that she's supposed to look like she's very aged. Compare the male and female portraits.
In Fate/stay night, the 'Obviously Good' female Servant, Saber, turns out to be the least sexiest out of the other enemy female servants. Really, compare her with Rider, or Caster (especially with her hood down), though Rider has the excuse of just merely being an opposing Servant, not aligned as evil like Caster.
Gilgamesh too, regardless of him being listed with a "Chaotic Good" alignment. And Archer in UBW.
Even though she's more neutral than evil, RougeTheBat should definitely qualify for this trope since she did willingly work with Dr. Eggman to help him in one of his many schemes to try take over the world in Sonic Adventure 2.
Dark Messiah has two possible love interests. The good one, Leanna, comes off as an annoying little sister and ventures dangerously into Scrappy territory. The evil one, Xana, is a naked succubus with the one of the sultriest voices every heard in a video game.
Used a few times in Chrono Trigger: Flea is the most obvious example, and there are also the voluptuous and seductive Naga-ettes (Mianu) complete with Femme Fatalons. On the flip side, there is Magus, who is possibly the closest Akira Toriyama has ever come to drawing a bishounen after Zarbon.
Sure, he tricked little children into doing his work for him and enslaved a country just because he was sick of the desert. Sure, he masqueraded as a god and helped a Psychopathic Manchild overthrow a peaceful realm. Sure, everything he touches seems to become corrupted. Nevertheless, Ganondorf in his proper Gerudo form still has thick red hair, muscles you could bounce a quarter off and skintight leather armor.
In Neverwinter Nights, Aribeth's blackguard armor looked a lot better on her than her paladin armor did earlier (ignoring the fact that they are identical except for a color shift). Also, in Hordes of the Underdark, the Elistraee-worshippers (good Drow) wear a lot more clothing than the Lolth-worshippers (evil Drow).
Neverwinter Nights 2 doesn't have very many examples, as most antagonists are undead or other sorts of monsters, but still has Bishop and Ambassador Claven.
Played either straight or subverted in F.E.A.R. 2: Project Origin. The precise answer to that question depends on whether you consider adult Alma to actually be evil as opposed to tragically insane, and whether you consider her naked adult form Fanservice or immense Fan Disservice. Helped and/or hurt by the fact that she ends up raping you at the finale of the game.
It's easier to say what villainous team admin, leader, or grunt doesn't fit this in Pokémon; though in several cases they're more so extremist than evil. The females especially tend to be Stripperiffic, and some of the straightest Bishōnen in the series are antagonists.
Arfoire from Neptunia is the personification of piracy, and piracy has never been sexier. The series reboot, mk2, introduces fanboy/fangirl personification CFW Magic, who wears a much more Stripperiffic outfit compared to Arfoire's.
Bad Girl of No More Heroes is arguably the most violent and psychotic character in the cast, and yet also wears the most fetishy outfit. She even sashays in it.
Jacqueline Natla from Tomb Raider. Even though they both save the world for selfish reasons in Underworld, Amanda Evert and Lara Croft could arguably be included as well.
In Archon Ultra, the good wizard leading the light side was an elderly man with a stately white beard and dignified white robes. The evil witch leading the dark side was a beautiful woman with raven hair, ruby lips, and a phenomenal figure that she was not shy about displaying in a revealing black gown◊.
The Bard's Tale nods to this when The Bard is confronted with the reality that Caleigh isn't a damsel in distress but a powerful, evil sorceress. His only remark about it is that she's actually sexier in her villain form.
Deckers Specialists, with their cleavage-baring tops, miniskirts and fishnet stockings.
Hatoful Boyfriend: Dr. Iwamine Shuu is portrayed human-style as an elegant older man with Purple Eyes, glasses, and long, curly brown hair. It's hard to see his actual form (a Chukar Partridge, dubbed "Fat Bird" by the fans) as sexy in the same way, but the player character seems to be attracted without seeing him as human.
Holiday Star makes it clear that Hitori Uzune, whom we'd grown to know and love in Nanaki Kazuaki's stolen identity, is also quite evil. Who'd have imagined a game about dating birds would include so many evil Bishōnen?
The Dominion of Wild Star is an entire faction of this trope. The Cassians aside, with their Eldan blood and good breeding, there is also the female Mechari and their poster-girl, Agent Voxine, and the female Draken and the numerous huntresses in Deradune, led by Huntress Kezzia. Serving the interstellar empire has some serious perks.
While in-game, both the Exiles and the Dominion are pretty morally ambiguous, you can't deny that the latter is more likely to get labeled "evil" than the former.
Carmen Sandiego is a famous thief, but she has this sense of charisma (and a lovely red coat) that makes her very attractive.
Drusilla, the succubus from Pibgorn, somehow manages to be a lot more seductive than the title character even though they are both attractive, slender women walking around (flying around?) wearing nothing but bodypaint.
Lucrezia Mongfish in Girl Genius, at least as she's played in the Heterodyne Shows and seen in flashbacks, dressed much more provocatively when she was evil than after she married William Heterodyne. After she possesses her daughter's body as The Other, the Big Bad of the series, one of the first things she does is strip to her underwear to admire the body she now controls and begin flirting with the son of her most ardent (and now dead) supporter with no shame whatsoever.
Las Lindas has AlejandraColdthorn, who is closer to The Rival, than a real villain, but still serves as an antagonist for her mean streak and some of her less than ethical actions, although this has been subverted as of recently.
Phil: You're changing alignment? But why? Dixie: Are you kidding? The perks are fantastic! Better hair — bigger bust — bitchin' outfits — plus I get my own minions!
Almost all the characters in Ménage à 3, of whatever moral standing, are more or less good-looking, but Senna, a raging egomaniac with a very distant relationship with the truth, is the one with the international modelling career. (Matt, who is merely a bit of a Jerk at times, appears to get slightly lower-level modelling jobs.) She certainly appears to think that evil is sexy herself; in her highly unreliable account of her relationship with her former assistant Sandra, planning treachery changes Sandra from a mouse to a vamp.
The main character of Doctor Horrible's Sing-Along Blog usually doesn't qualify, being a rather conservatively dressed and nebbishly awkward dork (albeit one played by Neil Patrick Harris). But during the song "Slipping" he takes a level in charismatic and holds a room in fearful thrall while singing in a quiet, hypnotic, borderline-seductive voice. Including leaning in and grabbing the chin of a bashfully frightened bystander to force her to look at him, in an almost Romanticized Abuse manner. Even lampshaded by the actress, who croons in the commentary that "This is my favorite scene."
Azula is built from the ground up with this trope in mind, and manages to be a spectacular example despite wearing (entirely practical) armor most of the time. Either that, or the creators hilariously misjudged how a lithe, sexy, raven-haired, busty teenaged girl who talks like The Vamp at all times would go over. (Fun fact: Grey DeLisle uses the same voice for Azula as she does for a BisexualVampire in Vampire: The Masquerade – Bloodlines.)
Chase Young from Xiaolin Showdown. Even his beast-form is sexy. And Wuya looks very nice once she gets a body. She even strikes some Male Gaze poses to seduce young Raimundo into continuing to work with her. Katnappe might also count.
When Elisa goes undercover as a crooked cop demanding protection money, she wears a black jacket, tight black pants, and a blue top that shows her midriff, displays cleavage, and nicely accentuates her breasts. No wonder she quickly charms mob boss Tony Dracon into letting her join his crew.
She's more morally ambiguous than Demona or Hyena, but Fox still counts on both the evil and the sexy - even the tattoo on her eye doesn't hurt. Especially if you like redheads. Her husband - David Xanatos himself - isn't an eyesore either, in a rather ruggedly-handsome way.
Post-timeskip AndrAIa was already hot stuff to begin with, but when she gets infected with the Daemon Virus she becomes downright seductive, going as far as calling Matrix "lover". Pretty shocking for a supposed kids' show.
Daemon herself. The accent is probably part of it.
Hexadecimal, when she's not wearing the scarier masks. Megabyte rebuilt her with a costume that featured a good deal of black leather. Her response: "WHO MADE ME LOOK LIKE THIS?! IIIII...like it."
Lady Frenzy in The Bots Master is a prime example of this trope, being a reasonably busty blonde with nice cleavage, a tantalizing front-slit skirt, and the phone-sex huskiness of voice artist Janyse Jaud (who also voiced Kagura in InuYasha).