Death Eater
The use of the Unforgivable Curses was authorised against Voldemort and his followers by Bartemius Crouch Sr, during the First Wizarding War. (Shortly after his resurrection, Voldemort names two Death Eaters "killed by Aurors".) In addition, in "Deathly Hallows", the Unforgivable Curses are used liberally by good characters, ranging from Professor McGonagall with the Imperius Curse, to Harry effectively using the Cruciatus Curse. He also uses the Imperius Curse on a goblin and a suspicious Death Eater during their disguised attack upon Gringotts Bank.