Favorite is especially difficult because it's so subjective. For meanest, I'd go with the White Witch for the line about asking the animals celebrating their visit from Father Christmas if she'd "like my dwarf to find your tongue with his whip." For most conniving and Machiavellian, I'd answer Lord Sopespian for murdering Miraz and blaming the Narnians out of his own sheer hunger for power.

For favorite, though, I'll have to go with the Lady of the Green Kirtle. She is introduced in a way that immediately creates a sense of menace, the description of a bright green snake the color of poison and then Rillian seeing and being charmed by a beautiful woman with a garment of the same color. What I truly find fascinating about her as a villain is that, in contrast to the White Witch who is so angry and hostile that as a reader I wondered how Edmund doesn't see it, she puts on a convincing facade of friendliness and desire to help the party of Puddleglum, Eustace, and Jill. In the final scene in which she tries to brainwash them into thinking that there is no sun and that the world above is a figment of their imaginations, she is even more chilling than the scariest and meanest dragon or giant because her power of seduction is so strong that her music, voice, and magical powers of persuasion almost seem like they're going to work. This is far more memorable, and teaches a lot more of a lesson, than if she had just immediately turned into a scary serpent like she would as the final boss in a video game. If Netflix does make a show or movie based on The Silver Chair, I hope they get the atmosphere of this scene right and get an actress who can seem both alluring and menacing and don't just turn it into an action battle with a scary creature.

What an interesting point, Tumnus!

Yes, the Lady of the Green Kirtle is a scary villain. She's also very mysterious; we don't know much about her, and we don't really even know what she was planning. She's got not only Rillian, but an entire civilization of gnomes, under her control. She can turn into a deadly snake, and (apparently) turn people's blood to fire (if her threat to Puddleglum was legit, which we can probably assume it is). Another thing both witches have in common is they threaten to do far worse than they actually do (thankfully for the heroes and Uncle Andrew ). But yeah, she is a very different character and one that needs to be done right. If she and Puddleglum are done well, the battle at the end will be way better than any video game.

PS: It's funny you mention video game boss battles, because as a game programmer myself, I have many thoughts on that subject; that's a whole other thread I would love to talk about some time.

PS2: Love your signature and avatar. Very cool.

Yes, the lotgk is a very scary villain... I remember the portrayal of her snake transformation in the Focus on the Family audio drama scaring the tar out of me when I was 11. I was also chilled by her control over Rilian's mind!
My hope for the film adaptation of this scene is that it be very quiet.... the snake should glide off to hide at first after transformation, and then always be slipping off into shadows as the characters pursue it, and then suddenly lashing out from the darkness after a tense pause or two. The room where it takes place would ideally be built like a cathedral or something, with lots if pillars and doorways to hide behind. Hopefully that would help avoid the 'boss battle' feel a little bit ( which would I presume be instant chaos as soon as she transforms) and maybe represent the way the Lady always hides in shadows and deceptions, lying in wait times strike.

My 3 favorite villains are Rishda Tarkaan, King Miraz, and The White Witch.

I think I'm going to go with Rishda Tarkaan because I don't think anyone has mentioned him in this thread. I think he deserves more attention than he gets as far as Narnia villains go.

I just love how at the midnight meeting, where Shift is talking to the crowd, and he is trying to say "Aslan" and Rishda tells him, "Tashlan". It makes me laugh whenever I read it or listen to it on the radio theater (You know how when you watch a movie, and you rewind your favorite part to watch again? I do that with this moment on the radio theatre). At that moment, Shift has lost control over Narnia, and Rishda makes him look like, I don't know how to describe it.

Rishda is a manipulator and willing to put aside religion to get what he wants. He's not the White Witch or the Lady of the Green Kirtle. He doesn't have a magic wand or a magical chair. No, he's clever and ruthless. He poisons what is right and true in Narnia with his cleverness and brute strength with his ruthlessness. He can be intimidating and strong when he wants to be, but when is thrown into the stable with Tash in there, it makes him look so small.