And as if by magic, here is the good list. Same rules, this applies to all villains in a given anime not just one individual.
Honorable Mentions
Rurouni Kenshin: Never seems to have bad villains but mostly forgettable.
Zoids Chaotic Century: One of my best memories of the show but I sadly forget what it was like being so long ago.
Strike Witches: They have the terrifying part down but nothing else.
10. One Piece
Shonen Jump villains didn't do well in these lists but One Piece saves them from being total outcasts; One Piece is one of only two anime to be able to successfully get away with goofy villains, the other being Ultimate Muscle.
9. Air Gear
The nature of Air Gear allows for some creative battles and villains, many of which maintain an air of mystery every time and don't leave you disappointed by the end result.
8. Pretty Cure
Never let the cutesy, goofy villains of Precure fool you, by the time you get to the finale of every season expect the stakes to be high and the fights to be intense, even the movies manage to pull this off. All this from a Magical Girl show but it's not the only one on this list.
7. Card Captor Sakura
You could argue that the cards aren't really villains but the trouble they cause are enough to be labeled as such, even when the ringmaster is revealed, the quality of the villains doesn't drop.
6. Sailor Moon
The major reason Sailor Moon holds up so well is that it has some bloody good villains. Many of my generation got chills from the Dr Tomoe arc, while many feel sorry for Beryl's main henchman as they die one after the other. And as ground breaking as Madoka Magica is, it doesn't have a patch on Sailor Moon.
5. Slayers & Lost Universe
Lina Inverse & Kain Blueriver can easily be billed as invincible but the villains in both shows can easily reduce both to their knees and very nearly destroy the world. That's a sign of good villains right there when an invincible hero is made to look weak.
4. Soul Eater
This anime really knew what it was doing with it's villains, psychologically terrifying both visually and mentally which compliments the art style very well.
3. Every Gundam Series except G Gundam
Gundam villains have always done a good job in making the heroes really scared of death and no hero has ever successfully claimed a convincing victory against them without losing important people along the way or even the hero themselves managing to stay in one piece mentally.
2. Neon Genesis Evangelion
Speaking of mentally crippling, every angel in Evangelion seems to cause extreme psychological trauma for the heroes in almost every fight. It's proof of how well the series holds up even after 20 years since the original.
1. Full Metal Alchemist
But if you want a good set of villains, come to Full Metal Alchemist. I'm of course referring to the Homunculus, the most ruthless villains to ever grace an anime, they are everything villains need to be: Terrifying, capable of worrying the good guys, defeated in an awesome way and just be a bad ass. Even more amazing is that they pull this off twice.
