Barty Crounch Sr.

Barty Crouch Sr. was the head of the Department of Magical Law Enforcement when Voldemort first came to power. Crouch was somewhat megalomaniacal and intensely preoccupied with presenting the appearance of respectability. Crouch was a narrow, inflexible man who stiffly followed the rules. Though he despised the Dark Arts, the lengths to which he was willing to go to disassociate with anything that might blemish his reputation led him to behave almost as cruelly as many on the Dark Side, and gave Aurors powers to kill rather than capture suspected Death Eaters who resisted arrest. He sent Sirius Black to the wizard prison Azkaban without a trial.
Crouch appeared to be the favorite to become the next Minister for Magic until his son, Barty Crouch Jr., was caught with the Lestranges, Death Eaters who were assisting Voldemort's rise to power and who had tortured Neville's parents with the Cruciatus Curse. Crouch gave his son a trial before sending him to Azkaban; however, according to Sirius, the trial was a sham, merely a public demonstration of how much he hated the boy. The public were sympathetic to Crouch Jr., and placed all the blame on Crouch Sr., accusing him of driving his son to join the Death Eaters because of his parental neglect. After the trial, Crouch lost much of his popularity and any chance he had of becoming Minister of Magic, and he was shunted sideways to a post as the head of the Department of International Magical Cooperation.
About a year After the trial, Crouch's terminally ill wife begged for her son's life to be saved, so Crouch abetted the two in trading appearances using Polyjuice Potion. Mrs. Crouch died as Crouch Jr. in Azkaban, while Crouch Sr. subsequently used the Imperius Curse to keep Crouch Jr. under house arrest. When Bertha Jorkins discovered the truth, Crouch Sr. silenced her with a powerful Memory Charm that permanently damaged her memory.
Crouch Sr. makes his first appearance in the series at the Quidditch World Cup in Goblet of Fire, when he attends the Quidditch World Cup with his house elf Winky as well as Crouch Jr., who is hidden under an Invisibility Cloak. Due to Winky's fear of heights, Crouch Jr. is able to slip away and steals Harry's wand to conjure the Dark Mark. When Winky is subsequently caught by Amos Diggory with Harry's wand, Crouch Sr. angrily dismisses Winky on the spot for failing to keep his son under control, as it was her idea to let Crouch Jr. attend.
Shortly thereafter, Voldemort and Peter Pettigrew show up at the Crouch family home, having found out about Crouch Jr. from interrogating Jorkins. Voldemort places Crouch Sr. under the Imperius Curse, freeing Crouch Jr from the Imperius Curse placed on him by his father, and forces Crouch to continue to appear in public as if there is nothing wrong. While still under the Imperius Curse, Crouch Sr. acts as one of the five judges at the Triwizard Tournament. However, worried that Crouch will fight off the effects of the Imperius Curse, Voldemort later has him imprisoned within his own house and has him communicate exclusively through supervised owl post. Despite this precaution, Crouch manages to break free of the Imperius Curse, and makes his way to Hogwarts, hoping to warn Dumbledore of what is happening, running into Harry and Viktor Krum in the Forbidden Forest. However, while Harry is on his way to summon Dumbledore, he unwittingly alerts Crouch Jr., who is using Polyjuice Potion to impersonate Mad-Eye Moody, to his father's presence. Crouch Jr. immediately goes to the forest, stuns Krum, and then kills his own father.