As she falls into all three groups, Professor, then Headmistress, Dolores Umbridge is probably the worst teacher at Hogwarts.
The evilest professor in all of Hogwarts is, without a doubt, Dolores Umbridge. Having nothing to do with Voldemort makes her level of cruelty somehow worse, as she was acting completely off her own steam.
Quirinus Quirrell revealing he was the one attempting to murder Harry Potter. Professor Quirinus Quirrell is the main antagonist of the 1997 book Harry Potter and the Philosopher's Stone by J.K. Rowling, and its 2001 film adaptation. He was a Half-Blood Wizard and the Muggle Studies professor at Hogwarts.
Quirrell tried to put up feeble resistance on occasion, but Voldemort was far too strong for him. Quirrell is, in effect, turned into a temporary Horcrux by Voldemort. He is greatly depleted by the physical strain of fighting the far stronger, evil soul inside him.
In an interview, Rowling described Snape's character as an "antihero". She has said that she drew inspiration for Snape's character from a disliked teacher from her own childhood, and described Snape as a horrible teacher, saying the "worst, shabbiest thing you can do" as a teacher is to bully students.
Peter Pettigrew Selling Out His Best Friend
This betrayal had the biggest damage in the series as it made Harry an orphan, sealed Sirius in Azkaban for twelve years, and led to all the deaths shown in the future when the Wizarding War resumed.
The Head of Slytherin is Horace Slughorn (who left the role to Severus Snape for fifteen years before taking it up again in 1996) and the House's patron ghost is the Bloody Baron.
Minerva McGonagall:
Professor McGonagall is head of Gryffindor house and is the Transfiguration teacher. If you've read Chapter One of Harry Potter and the Philosopher's/Sorcerer's Stone you will know that she can turn into a tabby cat!
Later in the year, McGonagall duelled with Death Eater Alecto Carrow during the Battle in the Astronomy Tower and later learned of Snape's murder of Dumbledore. McGonagall was initially appointed as Headmistress, but was demoted after Voldemort took control of the school and placed Snape as Headmaster.
Pomona Sprout is Professor of Herbology and the Head of Hufflepuff House.
Moaning Myrtle
Born in the late 1920s to Muggle parents, Myrtle Warren started her Hogwarts life in the early 1940s, where she was sorted into Ravenclaw.
Scarlett Hannah Hefner (née Byrne; born 6 October 1990) is an English actress. She is best known for her roles as Slytherin student Pansy Parkinson in the Harry Potter series, and as Nora Hildegard in The Vampire Diaries.
Blood purity
There had also been definite examples of half-bloods sorted into the house, including Tom Riddle, Dolores Umbridge, and Severus Snape. Harry Potter, a half-blood, was nearly sorted into Slytherin, but because he asked not to be, he was placed in Gryffindor instead.
Most Powerful: Voldemort
Voldemort's most powerful (and vile) exploits took place after he had already left Hogwarts, but throughout his school career, he had proven that his power was unlike anything the world had ever seen.
Lord Voldemort (Ralph Fiennes), aka Tom Riddle, was described by Dumbledore as one of the best students ever to graduate Hogwarts as well as "the most dangerous Dark wizard of all time." Before he had even learned about the existence of the Wizarding world, he was terrorizing his fellow orphans with impressive but ...
We also meet Tom Riddle, who is, as it turns out, the heir of Slytherin. Present only in spirit, he has all the same been controlling Ginny, and having her act as Slytherin's heir. We also meet the Monster of the Chamber, a basilisk.
Her real parents were Daneel and Dean Novak, Pureblooded wizards. Turns out Daneel was Tom Riddles younger sister, Daneel Riddle. Of course, the Riddles were related to Salzar Slytherin himself, and this made Hermione the living heir of Slytherin. The problem with being a female Slytherin heir, is that they're cursed.
Flora was sorted into Slytherin House along with her identical twin sister, Hestia, at Hogwarts School of Witchcraft and Wizardry at the age of eleven, and became a member of the Slug Club in the 1996–1997 school year.
But when they went to Hogwarts, everything changed. The pair were parted when the Sorting Hat placed Severus in Slytherin and Lily in Gryffindor, and while Lily thrived in her new, magical life, Snape was essentially placed in close quarters with the likes of Lucius Malfoy, Avery and Mulciber.
Angelina Johnson is a member of Gryffindor House. She is a tall black girl with long black hair, which she wears in plaits, and brown eyes.
Harry rejected Draco's offer of friendship, preferring to choose his friends for their personality rather than their pure-blood status. Draco was usually accompanied by his cronies, fellow Slytherins, Crabbe and Goyle, and enjoyed having power over other students.
She was just 14 when she died.
Myrtle's life was cut shockingly short when she was killed by the Basilisk at Tom Riddle's command.
He was a Gryffindor
Hagrid's Hogwarts house is never mentioned in the books, but, given his kindness, noble nature and bravery, it might not come as that much of a surprise that Hagrid was in Gryffindor.