This unnamed, “massive” Death Eater was part of the group that invaded Hogwarts where he did tremendous damage (HBP27). Possibly the same person as the “Brutal-faced Death Eater”. It was his Avada Kedavra that killed fellow Death Eater Gibbon when it missed Lupin. He cast the Incendio spell that set Hagrid’s hut on fire.
big blond Death Eater
First Introduced HBP27