Dark wizard

A Dark Wizard is someone who has magical powers and use them in a criminal way. He uses forbidden dark magic, such as Unforgivable Curses. He is usually a very powerful sorcerer.

The known dark wizards are:
 * Grindelwald
 * Voldemort and his Death Eaters

Fan usually speculate about Salazar Slytherin being a dark wizard. He was trusted by the other founders, but he's the one who hided the Basilisk.