The previous chapter has a more obvious example here (where her left hand is halfway down the page doesn't help her case).
More to the point, she's also probably the only villain in the series who's evil with no Anti-Villain tendencies or Freudian Excuse for her actions, which just makes her even creepier than most other bad guys.
The series also avoids any Unfortunate Implications about homosexuality because her target Setsuna has been in the Transparent Closet all along, and is one of the most popular, competent and genuinely kind characters.
It turns she has "interest" in Negi and Fate in addition to her well-known taste for Setsuna (and, to a lesser extent, Konoka and Asuna), making her a Depraved Bisexual instead of, or in addition to, this trope.
Mai-Otome itself had one in Tomoe. While most of the Coral Otomes loved Shizuru and looked up to her as a heroic figure, Tomoe was actually in love with her, and at one point attempted to kidnap and seduce her (in a decidedly creepy fashion). This, coupled with her mean-spirited attitude toward some of the other characters had turned fan support against her, though an attempt at a comedic makeover of her character in Zwei (similar to the one Shiho received in her transition from Mai-HiME) tried to soften the blow somewhat.
Ryofu Housen from Ikkitousen skirts this trope, though she can also be seen as a female Depraved Bisexual. Slightly subverted, as her girlfriend Chinkyuu is the one who brings up her Pet the Dog moments.
From Gao Gai Gar FINAL we have one of the 11 Soul Masters, Pillnus. She takes a special...interest in Renais/Renee, loving beating her in combat and putting her into...compromising positions. It's even implied she raped her.
Ran Asuka from Devilman Lady, who discovers and largely manipulates the lead character Jun Fudou, seems to be attracted to her, or at least her superpowers.
B-Ko Daitokuji from Project A-Ko is a textbook example. While she is never explicitly called a lesbian, her affection for C-Ko clearly goes way beyond "pure affection," and sends her into increasingly over-the-top jealous rages against A-Ko, eventually involving military-grade weaponry and an invading alien armada (even though A-Ko and C-Ko's friendship is clearly only platonic, a point which is utterly lost on B-Ko.) For their part, A-Ko and C-Ko's relentless failure to acknowledge or even notice B-Ko's crush is probably a contributing factor in B-Ko's rage spiral. By the last two movies in the original setting, though, she could be called a "Psycho Bisexual", as she immediately "falls in love" with the same handsome biker that A-ko has her heart set on. That could just be her taking rivalry to the extreme, and/or reflect her intense envy of A-ko. Ironically, her dimensional counterpart in the "Vs." OAVs is nothing like her, and is even on fairly good terms with her dimension's version of A-ko.
Magic Knight Rayearth II has the delightfully bipolar (dementedly schizo might be a better descriptor) and certifiably psychotic Nova, whose switch every few moments from sweet and childish declarations of affection to a raving engine of powerful magical destruction can be a bit jarring. Although the circumstances of her consuming longing for Hikaru and the origin of both her and her madness are rather unique and in her own case most likely constitute use of this trope as a justified one.
Asami Hoshino from Myself ; Yourself, who was so in love with Shuri that she ended up causing the very object of her affection to leave. Though not before defending her from an Ax Crazy old lady.
Subverted to a point in Cynthia the Mission. Big Bad Cybele is a cruel, evil sociopath who will has a tendency for cutesyness and being generally cheery and nice when she's not killing. She's also a lesbian, but there's nothing psycho about it.
Also a subversion from the same manga, Takaya Kanae is a sweet, kind, gentle schoolgirl who has kissed more then a few girls in her day. Not psycho at all by any means... until you get to her alternate personality, Shii, who is a psychotic, evil man who will do anything to protect the innocent Takaya, while leaving her mostly unaware of his protection.
In Suzumiya Haruhi , fourth book, the Asakura Ryoko of the Alternate Universeseems to have somewhat Psycho Lesbian tendencies towards Yuki. Given to that she's a normal human, yet still ends up stabbing Kyon to protect Yuki.
She even waits for her at the school at 4:00 AM!
And in the anime she seems even worse, sprinkling Yuki with blood from her knife as she dances around in front of her...
Kasumi Kisaragi, the vice-president in the 2006 version of Kujibiki Unbalance, especially in the manga adaptation, where she tries to kill Chihiro when a love potion causes her to be attracted to him.
Rio in Gamerz Heaven ...she doesn't seem to have any sanity whatsoever when it comes to Kyouko.
Yui from Fushigi Yuugi is speculated to be one of these for Miaka. "I couldn't find a place between you and Tamahome!", indeed!
Played for laughs with Chizuru Honshou of Bleach. Two words: "Karakura Raizer!" She is very disturbed in many ways which is best depicted when she asks what a little girls cup size is.
Liang Qi in Canaan is psychotically devoted to her adoptive "nee-sama" Alphard, and those who try to get in the way of the two of them being together tend to meet with her full Ax Crazy wrath.
There is also Hijiri the kids' teacher who turns out to be working for the series Big Bad and after fighting Kirie develops a similar attitude towards her. Before that it's mentioned that Hijiri had been obsessed with Miharu since childhood.
Nami in Aki Sora. She starts out with a Matchmaker Crush involving her best friend Kana and her brother Sora, but after the date she set them up on went far beyond her expectations, she confronts Sora that evening, shoves him down, stops just shy of cutting off his penis with some scissors ("Hey... can I have this?"), rapes him while fantasizing that she has a penis and is having sex with Kana, and threatens afterward to cut his penis off for real if he ever tells anyone.
Actually, even though she's extremely forward at first, she takes being rejected by Kirihara fairlywell, all things considered. It's after Youko is brutally murdered, seemingly by Hei, that thingsgetdangerous.
Kokoa from Rosario + Vampire is utterly obsessed with the vampire side of her half-sister Moka.
Akuha of manga season II is revealed to be one of these for Moka.
Double subverted with Suruga from Bakemonogatari who is dangerously in love with Hitagi. She is actually a perfectly pleasant person, even to Koyomi, her crush's boyfriend. But she unconsciously wishes that Koyomi would disappear, and when the sun goes down her demonic hand takes control over her and tries to grant her wish, which means trying to beat Koyomi to death twice. There's also the fact that she starts stalking Koyomi after he hooks up with Hitagi.
Urushira from Bondage Fairies Extreme. There's moreto her than that, though.
Zombie Loan: The school nurse from the first two episodes, also Koyomi's "other" personality Yomi has a definite fondness for groping Michiru's breasts and attempting to molest her. Though the Ass Pull-ed its way out of this one by saying that Yomi's spirit is actually that of a boy.
Pretty Face: Nozomi would go to great lengths to get Rando (as Yuna) into her bed.
Venus Versus Virus: Sumire, in Berserker mode! It's a little bit subtle as she is violent with the Viruses and more sexual (in a rape sort of way) with Lucia, as at one point she says they should "become one."
Also, Lucia appears to be this in the anime, when she stakes Sumire's boyfriend.
W Juliet: Nomura Tsugumi, Ito's senpai by one year, doesn't make it a secret that she wants "Ito-kun" for herself and can sometimes behave as a Psycho Lesbian for comedy relief.
Mao Nonosaka from Mirai Nikki. She helps Hinata in her scheme to kill Akise, despite the fact that Hinata was only doing it to gain her father's approval. After Hinata apologizes for taking advantage of Mao's feelings, she actually tries to kill Yukiteru. Hinata herself doesn't really snap until Yuno stabs Mao.
Uruka from Steel Angel Kurumi 2 for Nako. Uruka sees Kurumi as an obstacle to Nako and will try anything to remove Kurumi, even if it means asking her father to call upon the family's private army to take her down.
Chloe of Noir fits this, but only in her final appearance. She met the lesbian criteria the entire time, but she doesn't turn psycho until after Kirika rejects (or more accurately, fails to even notice) her advances, and then acts to protect Mireille from her, causing her to snap.
Reimi from Bamboo Blade has stalked Miyako from the shadows ever since the latter had brutally rebuffed the advances of the former's crush in middle school (though the two attend different high schools). It soon emerges that, rather than wanting revenge on the boy's behalf, Reimi had become enamoured with how cool Miyako looked; she even has nosebleeds when she recalls the incident. However, she's not exactly the most subtle of stalkers; during a kendo sparring session between the two schools, Reimi walks right into the dojo, claiming to be in the photography club, and spends the whole time taking pictures of the weary Miyako.
Kaguya Hime: Although a bondage-wearer perv, Maggey is nice enough to be mostly harmless (beyond groping of strangers), and Chun-Lan is funny more than anything... but Mayu can get seriously scary.
Hellsing: In the first anime, a Lesbian Vampire character named Boobanshee/Bubbancy (actually a corruption of a Baobhan sith, pronounced roughly the same way in Japanese) tricks the entire Hellsing organization, save Seras and Alucard, into thinking that she is Integra's sister, Laura (a reference to Carmilla). Later, she attempts to drink Integra's blood, and bites and licks her chest after partially undressing her, after which Integra realizes that she has no sister; shortly after Bubbancy is dispatched and Integra refers to her as Countess Karnstein (another Carmilla reference). She also licks Integra's blood from her hand after stabbing her.
Saki: Touka has a rather unhealthy obssession on Nodoka Nodocchi. "I'm going to lick you all over and savor this delectable favor" anyone?
Tactics: The yuki-onna in the first episode (When she's possessed by an aradama, anyway.)
Zero no Tsukaima: A Love Potion in season 3 episode 6 turns most of the girls into one of these. Also, Janette based on subtext. In the opening for the fourth season there's a part where Janette hugs a struggling Louise close and licks her face. And in episode 2 of the fourth season Janette licks Louise on the face again and practically flirts with her calling her "cute and innocent" after slashing her with a poisoned knife.
'Cockroach' Oki of Arachnid is an interesting case - her psychotic crush on the main character, Alice, actually makes her less dangerous, and soon results in a Heel Face Turn. Subsequently, she's still a Psycho Lesbian, but also one of Alice's only friends and most useful allies, thanks to her total lack of ulterior motives beyond getting into our heroine's pants.
A one shot yuri manga by the name of Rapunzel turns it Up to Eleven with not one, but two of them. One cuts off the hair of the other in a fit of jealous rage, and then the one who had her hair cut cuts outthe eyes of the other as revenge. To top it off, the girl who did the cutting of the hair let her eyes be cut outwhile smiling. At the very end, they're both shown smiling and holding each others hands in the conclusion. Love Makes You Crazy indeed.
The Lady Lemongrabs, from the Adventure Time Fionna and Cake comic book series. The "lesbian" part seems to be incidental, as they're the genderswapped versions of characters who were VERY Ambiguously Gay and happened to also be clinically insane.
The Daughters of the Amazon in Y The Last Man are frequently branded psycho lesbians by other women (they're certainly psycho, and have little use for men). Subverted in that a) we never see any lesbian behavior among the Amazons and b) discreet lesbianism (especially with male impersonators) quickly becomes the norm in a world deprived of men. One of the few openly lesbian characters simply describes the Amazons as "nutters who cut off their norks".
They're likely "political lesbians" - heterosexual radical feminists who "became lesbians" for ideological reasons. Many real lesbians don't like them because their stance reinforces the fallacy pushed by homophobes that homosexuality is a choice. Another complaint from quite a few real lesbians who have been in relationships with political lesbians are that political lesbians are often unenthusiastic about gay sex, which the comic is probably pointing out.
Inverted in the case of Victoria Hand in Dark Reign. She is a lesbian (or perhaps bisexual) and easily the most sane of all of Norman Osborn's subordinates (Osborn himself included), but that might not be saying too much when everyone else is a Psycho for Hire at best and Eldritch Abomination at worse.
This is the subtext to Ursula Imada's obsession with Sundra Peale in Nexus. By the time of Ursula's death, it was only just barely subtext.
Not the point of the alt comic Hothead Paisan: Homicidal Lesbian Terrorist; although it may have addressed this trope at times, it's more a spoof of Straw Feminist fears.
The sadistic Nazi Ingrid in Roberto Rossellini's seminal classic Rome, Open City (1945). Ingrid plies her targets with luxuries like narcotics and fine clothes in order to gather information on the Italian resistance in Rome; eventually disposing of them when they outlive their usefulness. The young woman she seduces doesn't come off too well either, but she's desperate, bitter, and impoverished in war-torn Rome and is somewhat easier to sympathize with.
Eve Harrington from All About Eve (1950). Not outright stated, but quite explicit for the era, including a one-scene Spear Carrier whose presence is all but impossible to explain any other way.
The Great Tyrant in Barbarella (1968), even hooking the titular character up to an Orgasmmachine, planning to kill her through death by orgasm. It doesn't work.
Sister George from The Killing of Sister George (1968) is pretty unstable, and very possessive of her lover. There's also her predatory boss Mercy Croft.
In the Spanish horror film The Blood Spattered Bride (1972), a young bride, uneasy about sex with her husband, encounters Lesbian VampireCarmilla and is seduced, and together they unleash murderous enmity toward men.
The Maids (1975) is all about this. Well, it has just three main characters: two are psycho lesbian sisters (the titular maids), and the third is their mistress who doesn't look very straight or very sane.
Andrea Glassen from Windows (1980).
The evil Queen Gedren from Red Sonja (1985) seemed visibly attracted to the titular character, before said character disfigured her.
Serial Killer Catherine in Black Widow (1987). Though she seduces, marries and murders wealthy men (ostensibly for their money, but long past the point where she would already be rich) there's a definite lesbian subtext with the female Justice agent pursuing her.
Rebecca (played by Leighton Meester) from The Roommate, which is essentially a remake of Single White Female.
Eunice from Butterfly Kiss (1996) is very much this trope; the only twist is that the girl she's obsessed with reciprocates her feelings, and they turn into an Outlaw Couple that wreak havoc in their wake.
Kate's Addiction (1999) follows Kate's obsessive pursuit of former friend Sara up to and including killing anyone who gets in her way.
Harris from Camp Blood (2000) went insane and became a serial killer after catching her girlfriend cheating on her with a man.
It's worth noting though that she comes off as more of the genuinely unbalanced sort, than the more Axe Crazy psychos that can be found on this page.
In Lost and Delirious (2001), the main character learns that her boarding school roommates are in love. One girl's family pitches a fit, and she goes to sleep with the first guy she sees, and the other girl goes completely insane, chasing eagles in the woods and she commits suicide at the end. It's even worse because the older teacher tries to save her by sharing her own forbidden love.
Paulie's much less palatable in the book: She not only dresses up as a guy, but deceives the entire school population into thinking she has a brother, but she worships King Kong and she strings (the much less naive) Mouse along much further. Her own sexuality is never mentioned, although there's a brief scene with Tori, who professes a crush on "Lewis". The older teacher is still in a forbidden romance (here explicitly stated when Paulie and Mouse find letters from the teachers), but this is better justified by deliberate Values Dissonance (the book's set in the 50's).
Parodied in D.E.B.S. (2003). The villainess Lucy Diamond is more than willing to sink the entire continent of Australia in frustration over not being able to form an emotionally satisfying lesbian relationship. Fortunately she is redeemed by the love of an incredibly hot secret agent in a plaid skirt. Then there was Lucy's blind date Ninotchka, who was clearly not all there and completely lost it when Lucy tried to back out of their date.
Jennifer from Jennifer's Body (2009) can be interpreted as being romantically attracted to her best friend Needy. When she becomes possessed by a demon and starts eating people, she specifically targets boys who Needy likes or loves.
Syl and Madie from Maskhead (2009) are a sick lesbian couple who make fetish porn that always ends with the participants being slaughtered by their pet killer, the eponymous Maskhead.
In Matilda, the Big Bad is a sadistically evil, authoritarian, and athletic monster of a headmistress named Trunchbull. In one scene, schoolchildren in a spelling lesson chant letters with the word "Mrs." added to set the rhythm: "Mrs. D, Mrs. I, Mrs. FFI..." the Trunchbull bursts out, with an annoyed expression, "Why are all these women married?!" The "bull" in the name Trunchbull probably implies "bull dyke," a common derogatory term for lesbians.
An early example, from 1895, is Mary Wilkins Freeman's story "The Long Arm" (probably inspired by the sensationalistic media coverage of the Mitchell/Ward murder case in 1892). Here, Phoebe Dole, a terrifying, powerful, manipulative woman, has been maintaining another woman in subjection for years, and when this woman finally takes steps to leave her for a man, Phoebe bloodily murders the hypotenuse, pinning the crime with diabolical cleverness on an innocent party. She attempts to justify her crime (in a Villainous Breakdown) by saying that she's defending her domestic happiness, but this "happiness" is presented as perverted. She's described as physically monstrous as well as morally — she's the one with the abnormally "long arm" of the title — as one critic put it, "a desperate figure of lesbian evil, a hypocritical, sick, self-absorbed carnivorous flower."
Mary Whitaker from the Lord Peter Wimsey mystery Unnatural Death (1927); though Sayers also presents a lesbian couple in an earlier generation, Agatha Dawson and Clare Whitaker, as not psycho and as having a successful relationship.
In Junichiro Tanizaki's novel Quicksand (1928), Sonoko Kakiuchi, a bored, wealthy housewife, is seduced by Mitsuko Tokumitsu, who proceeds to insinuate herself into Sonoko's life and utterly wreck it.
Subtext in Nella Larsen's Passing (1929). The egotistical, needy, manipulative Clare, a practiced seducer, uses her beauty and charm to fascinate Irene before setting out to take over Irene's life and husband. Irene eventually murders Clare while still attracted to her.
Mrs. Danvers from Daphne du Maurier's Rebecca (1938).
In That Hideous Strength (1945) by C. S. Lewis, the Big Bad is an organization that employs, among other baddies, a sadistically fascistic head of security named Miss Hardcastle, who is strongly implied to be lesbian.
Kathryn Hulme's The Nun's Story (1956) strongly implies that the Archangel Gabriel (an inmate in an insane asylum) is one of these, not least because her assault on Sister Luke appears to be attempted rape.
One of these features as a villainess in the Judge Dee novel The Chinese Maze Murders (1957).
The third book has Beebo kill a dog in order to keep Laura. It doesn't work. She wakes up to herself in the fourth book, by which time Laura has married Jack—although both of them remain gay—and had a daughter. Fortunately, Beth is there for Beebo.
Agatha Christie had one of these as the murderer in Nemesis (1971). The lady couldn't accept her 'protege' leaving her for a man.
In Daemon in Lithuania (1973), some characters put on a play that contains half of all the old-fashioned clichés ever invented. Kinga is found to be pregnant, and: "Enter the Lady-in-Black. She nourished a tragic passion for Kinga, and heaped the most terrible reproaches on her head, striding up and down the stage and drawing on her long cigarette holder. Finally, she tossed it on to the ground, stamped on it, and flung herself on to her frivolous friend's couch, intending to strangle her..."
Andrea from The Zone series (1980 - 2007) of World War III novels by James Rouch, is certainly (psychopathic if not psychotic) and is widely assumed to be a lesbian by the other soldiers because of her contempt for men. Eventually however she forms a sexual relationship with Major Revell.
Robert Westall's Futuretrack Five (1983) has a mild parody; Dronfield Biological Warfare Research Centre is staffed entirely by female Techs. All of the male Techs believe them to be Psycho Lesbians.
In Island in the Sea of Time (1998) and its sequels Against the Tide of Years and On the Oceans of Eternity by S. M. Stirling, the chief henchwoman of the Big Bad, William Walker, is Alice Hong, a psychotically dangerous, sadistic, and bisexual nurse, nicknamed the Lady of Pain.
Ruth Vigers in Affinity (1999) by Sarah Waters. An Evil Mastermind con artist who gets her jollies preying on young girls while dressed as a male spirit. It's implied she's something of a control freak with her girlfriend, femme moll Selina. Perhaps an attempt at deconstructing this trope, by putting it in a social context. The protagonist of the book, whose lesbian impulses are tightly repressed, is mentally disturbed in other ways.
It's also worth remembering that Selina was an accomplished confidence trickster long before she met Vigers, and only started working with Vigers in the first place because she convinced Vigers' mistress, Mrs. Brink, that she was Mrs. Brink's dead mother reincarnate. She only seems less culpable because her actions are viewed through her own eyes or Margaret's, and neither is exactly an unbiased observer.
Ktarka Zamlon Torin in Beyond Varallan (2000), the 2nd book in S.L. Viehl's Stardoc series, is first person in her planet's known history to have homosexual tendencies at all. The first lesbian in Jorenian history turns out to be a drug-fueled rapist and murderer with oddly vague reasoning for her infatuations...
DI Jan Shields in Val McDermid's The Torment of Others (2006) is a particularly nasty example who uses More than Mind Control on a succession of mentally-challenged young men to force them to kidnap and torture prostitutes for her viewing pleasure.
Subverted in HeroesThe audience is led to believe that Gretchen Berg is perpetrating acts of violence against anyone who tries to get close to Claire, including her roommate Annie and members of a sorority. She also Facebook-stalks her. However, though she did have a crush on Claire, it is revealed that the acts of violence were in fact perpetrated by someone working for the main villain, Samuel.
Mickie James from WWE started out as Trish Stratus's psychotic lesbian stalker.
Unlike many of the other examples, Mickie James was embraced by the fans. It helped that along with being a genuinely talented woman, she was funny in the role and likable.
In the episode "Good Night, Dear Heart" of Quantum Leap, Sam tries to determine the cause of death of a young woman who was apparently drowned. It turns out that the young woman was murdered by her lesbian lover because she fell in love with a man.
Several in the first two seasons of NCIS. Since the second season ended, their problem with Psycho Lesbians seems to have disappeared:
In "Conspiracy Theory", the killers turned out to be two women who had been committed to a mental hospital, where they now have sex with each other.
In "Lt. Jane Doe", a lesbian petty officer killed and raped her lover and then implanted semen from an old cold case into her so they would think the rapist had struck again. It probably would have worked if they hadn’t figured out the original rapist's identity. (In a bit of a Contrived Coincidence he had just gotten out of a Canadian prison a month before and moved back to Virginia). It turns out he had died a few weeks before the murder.
Legend of the Seeker has one in Dahlia, Cara's ex-girlfriend who betrays her, kidnaps her and tortures her into becoming one of the screwed up family again. When she kisses Cara (who is chained up, bruised and bleeding) and Cara head butts her, she does not respond to the rejection well, though fortunately all we get is her statement/threat that her previous torturer was 'being too gentle.'
Lydia Hart on Hollyoaks. After being dumped by Sarah, she sent dead flowers to herself pretending they were from her ex-girlfriend Charlotte, making Sarah get back together with her out of pity. Not long after that she tried to murder her love rival Zoe during a skydiving holiday by sabotaging her parachute, but the parachutes were handed out in a random order and Sarah was killed instead.
Mona in the TV show Pretty Little Liars appears to be this, as she tries and fails to get rid of the other three liars so she can keep Hanna all to herself.
Several characters of Cutie Honey the Live. The title character, Honey, is lusted after by another female main character, Yuki. Yuki gets extremely jealous and posessive although they never develop a romance, her insanity builds up to the point where she becomes the main villain. Additionally, another main character, Miki, initially appears to be somewhat insane (introduced in a prison, then slaughters a bunch of men attacking the prisoners; proceding to become a hero until her death, only to be brought back to life, only to be merged (in the midst of a lot of lesbian subtext) with Honey to help her defeat the Psycho Lesbian villain Yuki. That's not all, however; Mayumi, a sadist teacher who likes to perform an ambiguous lesbian sex act involving raw eggs on her students, develops a passionate attraction towards Miki, whilst fighting the heroes throughout the series. In the end, in Miki's last moments, she finally shares a kiss with her.
"Somebody's Watching," an early episode of Criminal Minds, had Maggie Low as the unsub, a college friend and longtime stalker of Lila Archer. She confronts Lila and Spencer at gunpoint in the end, furious because Lila and Spencer are attracted to each other.
The ITV Miss Marple adaptation of The Body in the Library actually changed the identity of the killer from Christie's original plot in order to cater to this trope.
Carmen on South of Nowhere is supposed to be portrayed as this but the worst thing she does is push Spencer into a wall by accident when fighting over the fact Spencer still has feelings for Ashley; and she immediately apologizes for it. She is popular in the fandom; instead of shipping her with Spencer, many people prefer her with Ashley's sister Kyla.
On iCarly, Missy is believed to be this and some people also view Sam as one as well, and their episode together made it look like two Psycho Lesbian's fighting for the love of Carly.
The video for Amanda Palmer's "What's the Use in Won'drin?" seems to be setting up a story of a battered wife who's secretly in love with a female friend until the last thirty seconds or so, when it makes a distinct turn for the darker.
The 1920 surrealist play Les Détraquées ("the deranged women") features lots of depravity in a girls' school, including two lesbians, the director and the dance teacher, who torture and murder a student.
The Miracle Worker alludes to Psycho Lesbians existing in the asylum which Annie Sullivan grew up in: "The asylum? [...] There were [...] some of the kind that keep after other girls, especially the young ones."
Inez in No Exit is a lesbian, and she's open about living for the pain of others, but her orientation seems fairly incidental to her character.
Amongst the Ax Crazy bosses of Dead Rising, Jo Slade stands out. A sadistic police officer who brutalizes young women, she was one of the creepiest enemies in the game.
Claudia Wolf of Silent Hill 3, possibly. She seems to be obsessed with Heather, or rather with Alessa, in more ways than one.
Played for squick in Haunting Ground, the (technically) asexualHomunculus Daniella could qualify. Insanely jealous of Fiona's Azoth and her ability to bear children, she gropes her in her sleep before breaking a window with her own forehead to get a piece of glass sharp enough to dismember the girl.
The Interactive Fiction game The Blind House has heavy subtextual hints at an attraction between its two main characters, Helena and Marissa, and both of them are clearly pretty unstable in different ways — but especially Helena, who has just killed a woman who is implied to have been her lover. What really takes it into this trope's territory, though, is The Reveal that Helena has been stalking Marissa and trying to trap her in her own house, and the fact that in one possible ending, Helena kills Marissa too. While lying on top of her on her bed. And then cuddles with the corpse.
Hirasaka Hatsune from Atlach=Nacha absorbs energy by having sexual intercourse with people or eating them. She prefers females for sex and males for eating. If you piss her off, she will tear you apart before devouring you... all with a smile, too.
Umineko no Naku Koro ni offers a rare mutual example with Lambdadelta and Bernkastel. At first it seems like it's Lamda's one-sided Mad Love that makes her want to keep Bern all for herself. In Episode 5 though, it turns out they have a genuine love for each other. Very violent and twisted, but genuine nontheless.
Yukari and Yuyuko from Touhou are like this in the 18+ version of the IOSYS fan video Border of Extacy. For general safe-for-work principles and sanity, a link shall not be provided. (A search on YouTube will not reveal this video but will reveal the other version of the video)
In Chloe's web comic Go Get a Roomie, "Roomie" of the title appears to manifest this trope: technically homeless, but playing on her charm and good looks to obtain rent-free stays with a string of lovers, taking them for granted for everything until she gets bored and moves on, generally wearing stolen clothes and with whatever money she can scoop up on the way out. It is only way into the series that it is revealed she does have feelings for others and a conscience, but the Roomie of the early strips is a heartbreaking conscienceless psychopath.
In YU+ME: dream Sadako is a pretty perfect example. That being said, other characters provide more positive depictions of homosexuality and bisexuality.
Lemon and Lime from Evil Plan. The inseparable supervillainesses refer to each other as their "wives," and while they seem to be happy and perky, the right conditions are all that needed to let the unsettling mania show...
One of Vanessa's exes in Something Positive, whom she left for casting aspersions on her bisexuality once too often, apparently still calls her, begging to get back together while calling her "whore."
Yuki, from Ménage à 3. Not only does she have a brain disorder where she sees all male sex organs as "Naughty Tentacles", but she has repeatedly attacked said "Naughty Tentacles" with the intent of utterly destroying them. She constantly turns the protagonist Gary's life into a living hell, forcing him to make out with his gay roommate and blackmailing him into helping her illustrate a manga. Yuki seems to be inching toward bi in recent strips, though, and has become somewhat friendlier.
Missy from The War Comms. At first she was just a lesbian who happened to be a psycho, then a psycho who happened to be a lesbian. Then she started making some suggestive comments about Esmeralda and Trisha, whom she claims to despise and, well.