Severus Snape lasted until the series' seventh book.
 At one point, Snape is named as a Death Eater by Igor Karkaroff, but Dumbledore comes to Snape's defence, claiming that although Snape had indeed been a Death Eater, he changed sides before Voldemort's downfall and turned spy against him
 In 2016, a fan film prequel, Severus Snape and the Marauders, was released online and Snape was played by Mick Ignis

