the best portrayal of a "villain" i have ever seen is the main character in a movie called wolf creek. i recommend it (not for it's violence, but for the actor's chilling and brilliant rendition of a serial killer)
just a quick scene description of the youtube clip below:
2 british backpackers team up with an australian young man and they are on a trip across australia. they visit a meteorite crater (wolf creek meteorite site), and while they are gone from their car, the psychopathic killer sabotages their car.
they return to their car and are unable to start it. as night falls, they decide to sleep in the car, but the killer turns up in a pickup truck, and acts like a friendly passer by who stops to "see what is wrong". he seems friendly but mildly gruff, and the english girls like him at first because they see him as more of a "man" than their australian young man friend. he "tries" to fix their car, but "can not", and so he says he can tow them to his place (few miles down the road) where he will fix their car. they reluctantly agree wondering if they will have to pay.
he tows their car for about 100 miles, and they are initially worried why he is taking them so far, but they wear it.
when they get back to his place, he offers them a drink around his campfire, and they eagerly accept because they are charmed by his extreme "australian outback" personality.
the following scene is the first scene in the movie where things start to go "pear shaped" for the backpackers as they try to overlook the quite worrisome personality change in the man.
it is only 54 seconds so you may as well have a look at it.
[youtube]http://www.youtube.com/watch?v=nT2qFx9iSlM[/youtube]