Corban Yaxley

Yaxley served Lord Voldemort as a Death Eater during the First and Second Wizarding Wars. At the height of the latter, when Voldemort was in control of the Ministry of Magic, Yaxley became the head of the Department of Magical Law Enforcement. He is known only by his surname and is described as having blunt features and an unpleasant smile.

In the Harry Potter and the Half Blood Prince film, he is played by

Battle of the Astronomy Tower
Yaxley was mentioned briefly by Severus Snape in 1996 and participated in the Battle of the Astronomy Tower in 1997. He was most likely the Death Eater Harry Potter stunned in the Astronomy Tower after Albus Dumbledore's murder.

Ministry Take-Over
Yaxley attended the meeting of Death Eaters at Malfoy Manor in the summer of 1997. During that meeting, he reported that he had placed Pius Thicknesse, then head of the Department of Magical Law Enforcement, under the Imperius Curse as part of Lord Voldemort's plan to take over the Ministry of Magic. Many of his fellow Death Eaters were impressed, though Voldemort believed Snape's estimate of when Harry Potter would be removed from his relatives' home over Yaxley's. Yaxley fell for the trap set by Alastor Moody on that count, whereas Snape knew the true date, setting the stage for the Battle over Little Whinging.

"You realize that I am on my way downstairs to interrogate your wife, Cattermole? In fact, I’m quite surprised you’re not down there holding her hand while she waits. Already given her up as a bad job, have you? Probably wise. Be sure and marry a pureblood next time... But if my wife were accused of being a Mudblood — not that any woman I married would ever be mistaken for such filth — and the Head of Department of Magical Law Enforcement needed a job doing, I would make it my priority to do this job, Cattermole. Do you understand me?"

- Yaxley intimidating Reginald Cattermole (actually Ron Weasley in disguise)

On August 1, 1997, Voldemort's plan and Yaxley's efforts succeeded when Minister Rufus Scrimgeour was killed and Thicknesse became the puppet Minister for Magic. The Ministry fell under Voldemort's control and Yaxley became the head of the Department of Magical Law Enforcement. In this role, he participated in at least some of the interrogations and harassment of Muggle-borns, along with Dolores Umbridge, head of the Muggle-Born Registration Commission.

When Harry Potter, Hermione Granger and Ron Weasley infiltrated the Ministry and freed the Muggle-born prisoners, Yaxley attempted to stop them. He grabbed Hermione as the trio Disapparated. Hermione managed to evade him by using a Revulsion Jinx, but not before revealing the location of Number 12 Grimmauld Place. Thus, the house was no longer a safe hideout for the trio.

Battle of Hogwarts
In 1998, Yaxley participated in the Battle of Hogwarts. He and Antonin Dolohov stood guard in the Forbidden Forest during the brief interlude that followed Voldemort's ultimatum to Harry Potter. They were followed back to the Death Eater camp by Harry under his Invisibility Cloak. During the final moments of the battle, Yaxley was defeated by Lee Jordan and George Weasley. He was presumably imprisoned in Azkaban after Voldemort's defeat.

Behind the Scenes
It is likely that Yaxley is related to Lysandra Black née Yaxley, wife of Arcturus Black I and maternal grandmother of Arthur Weasley, and thus to the Black, Crouch, Longbottom, and Weasley families, albeit distantly.