Bartemius Crouch Junior

Early Life
In 1981, shortly after Tom Riddle's first defeat, Crouch allegedly participated in the capture and torture of former Aurors Frank and Alice Longbottom with Bellatrix Lestrange and her husband and brother, using the Curse of the Cruciatus to drive them to madness. Crouch and his "accomplices" were sentenced to life imprisonment in Azkaban for crimes committed by his own father.

Crouch and his parents hatched a plot under which Crouch's mother would take his place in Azkaban, using the Polyjuice Potion to disguise herself. She died and was buried in Azkaban, with the result that the wizarding world believed that Crouch himself was dead. Crouch spent the following years living under his father's Imperius Curse. He eventually broke free with the assistance of Voldemort, who had learned that Crouch was still alive, and again entered the Dark Lord's service

Impersonating Alastor, former auror and new D.A.D.A professor at the Hogwarts school year 1994-1995. In this role, Crouch confounded the Cup to make Harry's name be picked out of the Goblet of Fire, and turned the Triwizard Cup into a Portkey. Harry and Cedric Diggory is teleported to Little Hangleton Graveyard.

Shortly afterwards, his identity was spread out in the community, and Crouch was given the Dementor's Kiss by a Dementor that then-Minister Cornelius Fudge had brought along with him.

However, when Christopher was killed in a car crash in Little Falls in 2012, he was resurrected by the stone, accidentally resurrecting many death eaters.

Illegal Relationships and Global Threat
When Crouch discovered that Christopher keeps driving out the many Dark Lords (Voldemort, Black, etc.), he decided to become powerful, comparing to Gellert Grindelwald, and took the true Elder Wand from Dumbledore's old tomb in Scotland (he managed to use Olivander under the Imperius Curse to transfer the wand's allegiance without Harry Potter's knowing), and became a Global Threat to the Wizarding Community by early 2019.