Laconic / Faux Affably Evil
aka: Evilly Affable

A villain with a fake, mocking veneer of niceness that only highlights their monstrosity.
Come, child, why don't you visit the unabridged version HERE before I ruin your life?

http://tvtropes.org/pmwiki/pmwiki.php/Laconic/FauxAffablyEvil?from=Laconic.EvillyAffable