Kathryn Merteuil

"It's okay for guys like you and Court to fuck everyone. But when I do it, I get dumped for innocent little twits like Cecile. God forbid, I exude confidence and enjoy sex. Do you think I relish the fact that I have to act like Mary Sunshine 24/7 so I can be considered a lady? I'm the Marcia fucking Brady of the Upper East Side, and sometimes I want to kill myself. So there's your psychoanalysis, Dr. Freud."

- Kathryn, explaining her frustrations to Sebastian Valmont

Kathryn Merteuil is the main antagonist from the Cruel Intentions duology. She's based on Marquise de Merteuil from the Pierre Choderlos de Laclos novel, Les Liaisons dangereuses. She is portrayed by Sarah Michelle Gellar in the first movie and by Amy Adams in the prequel movie.

In film
Kathryn Merteuil was born into money and daughter of Tiffany Merteuil in New York. Tiffany raised Kathryn to be manipulative as she is, though Tiffany did not openly approve this. When Kathryn was a teenager, Tiffany married Edward Valmont who's son, Sebastian Valmont was just as manipulative and dangerous as Kathryn. After a long standing rivalry, Sebastian joined Kathryn in her games of Manipulating the student body of Manchester Prep, and anyone else. However, little that Sebastian knew, she was only using him as a toy she likes to play with.

That all changed when a girl named Annette Hargrove moved into town. Sebastian and Kathryn made a bet that if he can get Annette to lose her virginity to him, he could finally sleep with Kathryn. However, if Sebastian failed, he would lose his vintage 1956 Jaguar XK140 Roadster to Kathryn.

Sebastian a long the way, fell for Annette and lost interest in Kathryn. Kathryn then manipulated him into breaking Annette's heart. After he came to collect his 'prize,' Kathryn finally revealed to him that she's been stringing him along all these years and that she does not 'fuck losers.' After which Kathryn manipulated a mutual friend of theirs to fight Sebastian. After he confronted Sebastian, a fight ensued. Sebastian during the fight was accidentally hit by a car. He died shortly after, telling Annette he loved her.

At Sebastian's funeral, Sebastian got his revenge from the grave when Annette published his journal revealing all of Kathryn's indiscretions (which included drug-use) to the student body and her mother and step-father. What happened after is unknown, but it can be assumed that she was kicked out of school and sent to rehab.

Alternate Ending
The original script's ending differed greatly. Instead of Annette publishing the journal, she uses the threat of publishing it to blackmail Kathryn into becoming essentially her slave. Corrupted by the tragedy she's been through, Annette plans to use Kathryn as a pawn to upset the social establishments at school and "turn it upside down". After kissing Kathryn forcibly, Annette leaves, taking Sebastian's car with her and leaving Kathryn defeated.

Personality
Kathryn's personality is a very complex and elusive one, the few who know the real her believe she is an emotionally unstable. She suffers from borderline personality disorder, and she's extremely manipulative and her charming and brilliant persona seduces everyone around her. Though very intelligent she has difficulty feeling empathy, sympathy, conscience, and is completely self-absorbed, not even appearing upset at her step-brother's memorial but making sure she look's perfect in the bathroom's mirror. Kathyrn is a psychopath because she has borderline personality disorder and shows many narcissistic traits.

Even before the events of the movie Kathryn was already accustomed to destroying her fellow peers' lives and using sex as a means to control the men in her entourage, but still maintaining that she is a virgin and is planning to wait until marriage.

Though Kathryn is self-obsessed (this may be a symptom of her borderline personality disorder), she isn't an actual sociopath (she does not have antisocial personality disorder), as she still has had feelings for a few men in her life such as Court Reynolds, a jock from her school who broke up with her on the 4th of July weekend in 1998 (who later fell for Cecile Caldwell, which led Kathryn to set out to destroy her life) and Ronald Clifford, Cecile's music tutor who's romantically involved with her, and with whom Kathryn openly sleep's with. After finding out she had been dumped by him she seemed to look mildly upset. She also seemed to genuinely love her brother back when he was on her side of evil, and his transition to good was seen by her as a betrayal and caused her to hate him, although she showed a small measure of regret when saying "Goodbye, Sebastian" after their final meeting. She also cries at the end of the movie when reading Sebastian's journal which describes every hateful facet of her personality yet still has "My True Love" scribbled by her picture, showing how Sebastian truly cared for her even so.

Kathryn also suffers from Bulimia Nervosa and is mildly self-conscious about her body. According to her, a great degree of her underhanded behavior is because of the double standard society places upon females and sex. Pretending to be a virgin and a good girl fills her with self-loathing, and she expresses that she sometimes feels suicidal as a result. Her cocaine addiction is her method of dealing with this.