Ghostface is a great villain, not least because no matter how many times you kill the guy/girl/stack of Little Rascals stuffed into the costume, he can always come back. Consistent throughout the films is the killer's voice, provided by Roger L. Jackson (infuriatingly no relation to Samuel), who can freak a girl out over the phone like no other except for Mel Gibson.
Props to Vader-he kept going when most people would have thrown in the towel long ago. After losing his wife and children AND legs AND BEST FRIEND in the course of an afternoon, Anakin wasted no time, strapping himself into an evil android suit faster than you can say "Hey, why don't we do the tiniest amount of research into the whole 'your wife is dead' thing that weird lizard guy definitely just lied to you about". You've got to want it.
Human meets robot, robot immediately tries to kill human, robots are evil always. It's a tale as old as
whenever robots were invented. HAL 9000 and The Terminator don't have much in common, but get them in a room together and you can bet they'll be simulating laughter and camaraderie as they plot to violently assassinate humankind. Good luck with that, guys, how are you going to get any human killing done once all the humans are killed? Idiots.
The creepiest thing about Keyser Soze is, as long as you're not one of the people who have had the ending ruined for them (and are therefore either in a coma or are literally using the internet for the first time ever. Hey! How do you like it so far?), Soze could be anyone, and anywhere. His presence hangs over the movie like a scary invisible nightmare ghost. As that old saying goes, fear of the unknown is worse than fear of the cute little guy who walks weird.
Maybe the worst thing about Norman Bates was he was kind of a shitty murderer. He left his house unlocked, filled with literally every clue you need to put together that he might not be holding up so great in the "doing a bunch of undetermined stuff with your dead mother" department. Sure, he had the basics down to pat: A costume, insatiable blood lust, saying the absolute creepiest things possible as every opportunity. It never quite came together, but damn, if he didn't try.
Marsellus Wallace, despite being an inexcusable asshole, really has a shitty day during the events of Pulp Fiction: He gets double-crossed, his wife nearly dies, he gets hit by a car, he gets
romanced in the sex dungeon of what is probably the least creepy pawnshop in LA. At the end of it all, though, he's still standing, and he's still an asshole. Respect.
These days, being a poor healthcare provider means nothing more than being a hospital that exists in the United States (ZING). Back in the 60s, folks were kinder, but that didn't stop Nurse Ratched treating every single patient under her care with total sadistic contempt. Her group therapies were exercises in cruel humiliation, and her "lobotomize everyone who gets in my way" policy seems a little harsh. There's no doubt Ratched was a driven career woman, she was just really kind of a dick about it.
Credit where credit's due, when the answer to "There's a crazy evil shark in the water" is anything other than "let's not go in the water then" and is more along the lines of "Let's stop at nothing to destroy it", you've really overcome the limitations of being a tiny-brained sea creature. Congrats on breaking through the glass
floor. Of those weird tourist boats.
Biff Tannen just sort of toes the line for most of Back to the Future. He's a shit, but not really the kind of evil we're looking for when it comes to a big bad movie villain. Then he straight-up tries to rape a girl in a parking lot on Prom night. This kind of reflects badly on everyone else in the movie, too. Like, how about we stop laughing at this guy getting poop dumped on his car and, I don't know, put him in prison? Way to ruin a perfectly good movie, Biff.
When it comes to ranking bad guys, it's hard to argue against "embodies the very nature of evil" as a qualification. Voldemort doesn't have much flare or personality, but he gets shit done. His best friends are snakes. He Mutilated what was left of his soul in exchange for raw power. He literally came back from the dead in an eighteen-year plot for revenge against a baby because it embarrassed him. He's the best at being the worst.