Walden Macnair

Walden Macnair was one of Voldemort's early Death Eaters until his downfall when Macnair claimed he had been put under the Imperius Curse, and went to work in the Ministry of Magic as executioner for the Committee of Disposal of Dangerous Creatures. He was present during Buckbeak's trials and was assigned the job of executing him. He partipated in the Second battle of Hogwarts, where he was thrown against the wall and knocked out by Hagrid (presumably because Hagrid recognized him).