How about Mildred from Of Human Bondage?
My #1 fave murderous, amoral, ass-kicking bitch: Lena Olin as Mona DeMarkov in Romeo Is Bleeding. Gentlemen, she may give you nightmares. Ladies, she may give you ideas.
Also, a nod to all of the villainous bitches in the Kill Bill films.
Dunno if she’s been mentioned: Rhoda from The Bad Seed.
Mrs. Danvers from Rebecca and Lady Catherine de Bourgh in Pride and Prejudice.
Thanks!
Again, I am the Poster Child for Fighting Ignorance. 
Oh yeah! Uma Thurman’s character in Kill Bill.
The Bride.
Beatrix Kiddo
Amazing! I just finished Season 3 on Netflix (I saw it before when it was running weekly as first run) last night (actually early this morning) and was so moved by the way Stahl was disposed of that I had thoughts of starting this very thread, or one that focused on the demise of the bad guys/gals in particularly memorable ways. Jimmy O got his in the same episode and it was great, too.
Stahl is who I thought of when I read the title. The next to hop to mind was Glenn Close in Fatal Attraction and I’m sure I will agree with others as I read the rest of the thread. I just had to comment as soon as I read the OP, since that’s so fresh on my mind!
I can endorse all of these, but I still favor Stahl as the main bitch. Ally has such weird eyes and such a venomous personality that acting Stahl was probably a piece of cake for her. Ever since her first scene, I kept hoping for something bad to happen to her, and having Opie be in on it a whole season’s worth later just fulfilled all the pent-up hate I had developed for her. That catharsis theme is being well exploited more and more in the shows I enjoy watching!
007 films: Fiona Volpe, Helga Brandt, Octopussy, Elektra King, Xenia Onatopp, Fatima Blush.
Rosalind Shays on LA Law
Cersei isn’t smart at all; she’s devious but frequently outwitted.
In a way, though, that makes her a great villain. She’s on the wrong side of things because she acts to defend things she’s emotional about, not because she’s “evil.” Cersei Lannister truly believes she’s right. It makes her seem real.
It’s easy to make someone just “evil.” Why is Isabelle de Mertueil evil? Why, because she is. She’s just a psychopath. And hey, they can work really well, as in many examples cited ths far, and someone it’s the right way to go - Darth Vader is a far more compelling villain when he’s just Darth Vader than he is when he gets a detailed explanation. Making someone a villain without being evil, though, that’s a really neat trick, and George R.R. Martin does it with several characters; Cersei Lannister being one, and Danaerys being another.
She may be “just evil” but the Evil Queen in Disney’s “Sleeping Beauty” is my nominee for a great female villain. That scene where she turns into a dragon gave me the shakes when I saw it in the theatre - & I wasn’t even that little!
And how could I forget Felice from Julian May’s The Saga of Pliocene Exile?
Vriska Serket from the webcomic Homestuck, although she sort of straddles the line between villain and protagonist. She’s an antagonistic protagonist, if that’s even a thing.
Everyone loves Vriska. Well, some people hate Vriska. But they love to hate her. But yes, she’s absolutely the villain, and I at least cheered when Terezi took her out.
But the best female villain has got to be, as was said above, Livia from I, Claudius. Not only is she the best female villain, but she’s one of the best female characters in any work of fiction - so say I.
Lady Eboshi from Princess Mononoke is a great character though she is perhaps not a clear-cut villain.
High on my list of movies I would like to watch which will never get made is a prequel about how Eboshi gets to become leader of Iron Town.
One of the great things about that movie is that it doesn’t really have a villain, just heroes who are nonetheless opposed.
Not to blur the boundaries between forums, but my nomination is GLaDDOS from the Portal games. Underneath all that sarcastic snark about trying to kill you in various gruesome ways, she really is trying to kill you in various gruesome ways.
Glinda the Good Witch from The Wizard of OZ. Undeniably, the most devious villian ever put on screen.
The Baroness.