Hm, I dunno - I always found polite, charming bad-guys a lot more sinister and spooky than ones that were all out crowing stupid. Ones that resort to yelling and screaming if the protagonist isn't doing what they wanted just make me think of a child throwing a tantrum, and while they make you jump (in a movie, for instance) I really don't find them scary for long - once the surprise has worn off, f'rinstance.
On the other hand, take the Tooth Fairy in Red Dragon, or Norman (whose second name I've forgotten - not Bates,
) in Stephen King's "Rose Madder" - most of the time they were pretty "normal", polite and with the potential to be really nice - it's only when they snap that you see how mad and dangerous they are. If the character is a little psychotic, I suppose, you could give them the undercurrent of unlikeability you wanted.
As a sidenote, the only character I've recently wanted offed in a film was Brab Pitt's character in Fight Club (which I only saw recently) - he IRRITATAED HELL OUT OF ME and I wanted him to be OFFED at the earliest opportunity.