Dermot Marranga

From Witcher Wiki

Dermot Marranga was raised in Kaer Morhen as a witcher, but he became a renegade, hired help in the city of Aedd Gynvael, where Geralt met him.
Killing humans and elves for money only gained Dermot certain death at the hand of Geralt.

Played by Tomasz Sapryk.