Affably Evil/Playing With

Basic Trope: The villain is still very much evil, but is a nice, ordinary person besides his villainous traits.
 * Straight: The guy looking to dominate the world is actually a very nice, pleasant person to know, as long as you don't get in his way.
 * Exaggerated:
 * He is indeed a very polite person. This is not an act, it is how he really is. Meanwhile, he plots with Satan to help cause the bloody and torturous eradication of all life.
 * The villain is so nice, that he donates blood, plays with young children, and hosts a birthday party for the hero, while preparing to launch a nuke at Australia.
 * Justified:
 * The villain is a little misguided and thinks he's doing the right thing, being an ordinary person, and so this is how he acts.
 * The villain is a Sinister Minister, Grand Vizier, or other person in a trusted position; even if his niceness is an act, he wouldn't be where he is without it.
 * The villain is so nice that no one believes he's doing anything villainous, in spite of blatant evidence to the contrary. This was part of his plan all along.
 * Evil is not mean. Mean is not evil. For more information, see Anti Hero.
 * And he wants to be/already is a Villain With Good Publicity. He decides that the only known way to do so is to be nice.
 * Anti Villain / Noble Demon
 * The villain believes that he can't let the fact that he is evil be used as an excuse to be mean.
 * Inverted:
 * The total Jerkass is, in fact, firmly allied with the hero and the cause of good, despite oftentimes having no heart of gold to show.
 * Good Is Not Nice.
 * Jerk With a Heart of Gold
 * Faux Affably Evil
 * Subverted: The villain looks like a kind, polite person, but it's all an act.
 * Double Subverted:
 * ...But the act itself was an act to restore his cred as an evildoer. He's actually a pretty nice guy.
 * The villain decides that being nasty to everyone all the time is too much effort and leaves him lonely, so he starts being more friendly to his minions and foes. This terrifies them even more, as they're waiting for the other shoe to drop.
 * Parodied: The villain ponders being nice for a change...and promptly rejects the idea, laughing evilly all the while, in favor of scaring people into submission as usual..
 * Deconstructed: The villain is so affable that he actually wins thanks to his ability to get along with others, while the Anti Hero drives away any possible allies he may have had.
 * Reconstructed: ...but only temporarily, as the villainy comes to light before the Point of No Return.
 * Zig Zagged: The villain looks like a polite person. It's an act. No it isn't. Wait, yes it is. Can he make up his mind already?
 * Averted:
 * The villain is rude, plain and simple.
 * Complete Monster
 * Enforced: The author is trying to deliver an Aesop that evil comes in all shapes and sizes.
 * Lampshaded:
 * "For a villain, he acts a lot like a normal person."
 * "I may be your enemy, but that doesn't excuse being uncivil."
 * Invoked: The villain tries to become a nicer, more polite person, in order to improve people's opinions of him, even if they do see his goals as "evil".
 * Defied: "I will not serve dinner for my prisoners! I'm evil, damn it, and I'm going to be a dick!"
 * Discussed: "All right, time to go confront Overlord Steve! Even though he's evil, I'm sure he won't mind if we drop by and have a chat." "Alice! He's not some friendly movie villain, he's evil."
 * Conversed: "It's weird how, in some movies, the villain is a totally normal guy except for his evil plots. Kinda makes you paranoid, right? Anyone could be evil..."

You're most welcome to head back to Affably Evil any time you like. But I won't take "no" for an answer.