[FairyKing]

I think my best would be either Evolt or Horobi, for pretty much the same reasons everyone has already said. But I want to talk about someone who hasn't been mentioned yet: Mitsuaki Gamou, AKA the Sagittarius Zodiarts, from Fourze. It's been a while since I saw Fourze so I don't remember him in perfect detail, but I remember liking how he could be so blatantly evil while scheming in his secret villain lair and then go out into the school and flawlessly switch to being the benevolent, respectable principal who inspired students to reach for the stars. It didn't come as a shocking twist like Evolt since they revealed pretty much right away that he was the main bad guy, but it definitely gave him a nice sense of menace and manipulative-ness.

For worst villain, either Kaito Kumon, who started out an interesting character until his philosophy devolved into "whatever the plot requires it to be," or... whatever nonsense was going on in the last arc of Ghost. Some kind of giant eye thing? Made by combining the generic usurper prince guy's clones with the monsters who were reused so often that even the heroes started to see them as just a chore? And it was all made possible by the plans of evil Steve Jobs? I still think Ghost had the potential to be great, but the execution was a mess and the ending especially so.