In ''Umineko no Naku Koro ni, Bernkastel is the worst offender. Starting at the end of arc 4, she ends up with quite a laundry list of horrendous acts. Conspiring with Lambdadelta so that Beatrice is their own personal plaything is the least of these. In arc 4 alone, she sets Ange up to have her life screwed over by the irredeemably fucked up at that point Eva and finds the result amusing. And for all her trouble, how does Ange get rewarded? By being RIPPED APART and presumably left that way. Bern and Lambda even JOKE about it. To top it off, Bern's only regret is that she lost a big advantage.
And of course, she ramps this up in Arc 5. She invokes Decoy Protagonist and Hijacked by Ganon when Battler refuses to play along and pulls out an actual Expy of Rika named Erika Furudo to serve as the new Protagonist. And Erika herself is a Bitch in Sheep's Clothing who immediately points the finger at Natsuhi, who currently is not having a good day. Which gets WORSE, now that being implicated for the murders brings her sister-in-law Eva's wrath down on her as the victims include her husband and Morality Chain, Hideyoshi. She also leads Battler to the Gold Room, which makes him the next successor, adding fuel to the fire regarding his family's stake in the murders. And manages to successfully disprove Beatrice, with Battler unable to help since he's too busy being IMPALED. Then Lambda makes Battler the Golden Sorcerer, effectively cementing him in the role of the 'villian'. And you know what the best moment of this is? Battler and Beatrice's furniture give Erika and her minions the beatdown they deserve. Naturally, Bern revels in this, until the point where Erika gets her ass kicked. She even has a smug 'Oh, did I piss you off?' look on her face at times.
And Arc 7 brings a huge surprise... Ange's parents/Battler's dad and stepmom, Kyrie and Rudolf, were this, not the Cool Big SisYandere and the Handsome Lech we thought they were. No wonder Ange has an Heroic BSOD after finding out and Beatrice herself opposes them. Though Bern might have something to do with it...
Kyrie arguably comes up as the worst in this case, though. As if killing the whole Ushiromiya family and servants was not enough, she also declares she doesn't love her own daughter Ange and would abandon her if her husband is not alive anymore, since she has no more use for her.
And Eva, who was thought to be the worst complete monster among the family and only survivor outside of Battler, due mainly to the events of Arc 3? It turns out it was all a fabrication so that she could paint herself as a complete monster just so Ange didn't have to know that her own parents were, in fact, complete monsters, by claiming she murdered and tortured everyone just so she could get the inheritance. So in the end, Umineko's reigning queen bitch turns out to be willing to allow Ange to hate her just so she doesn't have to know the truth.
Lambdadelta could qualify for the CM list, since she tried to make the fight between Battler and Beatrice last forever, all to "trap" Bernkastel.
Also, it has been implied that she helped Miyo Takano in her conquest of killing Rika and becoming god. This was brought up by an interview with the creator of both visual novels.
Aw, no mention of Eva-Beatrice? Sure, she's cute and all that with her Ambiguous Innocence, but admit it, she's also pretty scary and nasty as well. The main reason why she qualifies is that she loves torturing and killing other people over and over again in the most gruesome and embarassing ways possible. So basically, she kills one person in a brutal and playful way, big deal. Then she revives that person just so she can kill him/her again. Repeatedly. Until she's completely and utterly satisfied. Not to mention, when Beatrice tries to remind her that she told her not to be too cruel with her murders, Eva-Beatrice just tells her off. And what better example of one of her cruelest acts would there be without any mention of breaking her promise to Eva not to kill Hideyoshi because she's annoyed by his attempts to knock some sense into her after she orders the Siestas to kill Rudolf and Kyrie? Yeah, this girl's a monster.
At least, until EP 8, where she reveals that she actually cared for Ange despite hating her. Cue Love Redeems.
But does this really count for the people that she killed before this was revealed?
What about Erika!? I was convinced she'd be the one hiding under the spoiler tags up there! Let's see, what starts out as a seeming lack of tact turns out to be an obsession with intellectually destroying everyone around her and driving them to submission - a skill she first unleashes on Maria. She takes absolute, sadistic glee in her attempts to deny Beatrice and to "prove" the crying, helpless Natsuhi is the culprit, tortures her underlings when they fail her, murders the six victims of the first twilight in EP 5 by severing their heads (including Maria, whom she kills after disposing Rosa in front of her), and announces that she committed the murders with a pleasant smile. And she gets even worse in EP 6, where, among other things, she traps Battler's consciousness in a logic error and nearly forces him to marry her, fully intending to repeatedly rape his helpless body and make him watch from the logic error hell.
