It's a one-shot character but in the ITV-produced series Agatha Christie's Marple, the killer in "Towards Zero" is a fantastic depiction of a psychopath.

Superficially charming so that those who don't know them, but those who are intimately familiar with them are aware that they are deeply disturbed and would prefer to stay as far away as humany possible if they could. They are very good at looking civilised and cultured, but when they are exposed as the killer, that illusion instantly gives away and it is outright terrifying. And the true motive for the murder is so petty that the only person who knew them truly was also the only one not surprised by it - everyone else couldn't believe it