Throughout the Harry Potter series, fans see a lot of the classes that witches and wizards can attend at Hogwarts. Harry, Ron, Hermione, and friends go through many different classes with numerous professors. Some professors attended Hogwarts when they were young and came back to teach because they loved it so much, but others, namely the long line of Defense Against the Dark Arts teachers, were hired in the position because the school couldn’t seem to keep a professor for more than a year.
Each brought something new to the school, with some being wholly likable, friendly characters and others displaying more nefarious actions and attitudes. From Herbology's delightful Professor Sprout to polarizing Potions teacher Severus Snape, some of Hogwart's professors were certainly more evil than others.
Rolanda Hooch
Hogwarts has many classes focused on the lives of witches and wizards but it also has a physical education class reminiscent of a muggle school, taught by Rolanda Hooch. There isn't a more qualified witch to teach all things related to Quidditch. She has the right amount of patience and a sternness about her that fits the role of the P.E. teacher everyone loves perfectly.
When it's all said and done, Rolanda Hooch could never be evil. She'd always be out there rooting equally for every team and making sure it's a fair game.
Pomona Sprout
The Head of the Herbology department at Hogwarts, Pomona Sprout, does not play as big of a role in the movies as she does in the books. However, Sprout is one of Hogwarts' best professors.
She quickly notices Neville's knack for the subject and helps nurture his talents. Professor Sprout also proves to give pretty straightforward instructions during her classes but isn't as strict and stern as other professors. While her magical abilities aren't really shown in the movies, she is a strong witch, but could never turn to the side of evil.
Sybill Trelawney
One of the most curious professors at Hogwarts may have been professor Sybill Trelawney. As the Divinations professor, her class is unlike any other the students at Hogwarts took. Learning to read into the future has the possibility to lead to evil tendencies, but Trelawney doesn't seem to have an evil bone in her body.
Maybe it's her whole demeanor or the fact that she just respects the divination readings enough to not do anything bad with them, but she also doesn't seem to have the ability to be mean, let alone evil.
Filius Flitwick
The headmaster of Ravenclaw, Filius Flitwick is quite the character. He was also the Charms master as well as the choir director, and while there aren't many moments that fans actually get to see him use magic, there are plenty of ways Flitwick is Hogwart's best professor.
He is not known to be a strict professor and is one to secretly root for some level of silliness, as he silently cheers for the Weasley twins as they escape from Dolores Umbridge. Flitwick displays no actions that suggest he has any level of evil within.
Rubeus Hagrid
Rubeus Hagrid may be part giant, but he's as gentle as they come. With his teary outbursts and his knack for giving big hugs, Hagrid may be one of the kindest characters. He always cared about the creatures he took care of as if they were his own children.
Hagrid also constantly did all he could to help Harry and his friends, even if he knew it might get him in trouble. The only "evil" things he did was to get back for people hurting his loved ones, and even those actions (giving Dudley a tail, hurting Karkaroff for insulting Dumbledore among others) were minor compared to the actions of other Hogwarts professors.
Minerva McGonagall
Gryffindor's headmaster and the Transfiguration professor, Minerva McGonagall, is a powerhouse witch. She is stern but caring. Ever since Harry was placed in the care of the Dursleys, McGonagall had been on his side.
She never waivers from the side of good, and always battles evil no matter what size, shape, or form it comes in. She is one of Dumbledore's, and Harry's, most loyal friends and proves it until the very end.
Remus Lupin
Remus Lupin has the whole werewolf situation going against him. Since he can't really help what happened when he turns into a werewolf, he does have that evil aspect, but otherwise, Lupin is one of the most sincere, and kind-hearted, characters in the whole series.
When he becomes the Defense Against the Dark Arts professor, he plans the class to be taught in a way that would help Harry in his battle against Voldemort. Lupin's quotes full of wisdom are some of the best and show his true, and good, intentions.
Albus Dumbledore
Between lying to Harry, ignoring his warning about Snape, and quite honestly raising him knowing he'll end up dying, Dumbledore may not be the stand-up man fans of the series initially thought.
Dumbledore may not be fully evil since he does protect Harry and helps him on his journey, but he definitely does some things that are also couldn't be considered the actions of a truly good person. Arguably, leaving Harry with the Dursleys was one of the evilest things he did and is one of the reasons Dumbledore is Harry Potter's true villain.
Horace Slughorn
Unintentionally evil: that is the only way to describe Horace Slughorn. He seemed to live his life in ultimate fear and guilt when he realized what he had done by teaching Tom Riddle about Horcruxes.
He may be a bit of a coward - since he ran from Hogwarts when he thought Dumbledore would connect him to Voldemort - but ultimately he is a pretty nice guy. He gets excited when students are learning well, and continues to encourage those that still aren't getting things.
Severus Snape
Severus Snape seemed to tread the fine line between good and evil for the duration of Harry Potter. It wasn't until he showed that his Patronus was a doe in dedication to Lily Potter whom he loved with all his heart, that fans saw that he was ultimately on Harry's side.
While he may have taken the good side in the end, that doesn't necessarily excuse all the bad stuff he did during his time as a Hogwarts professor, including bullying and mistreating students. Not only Harry but Neville and Hermione were frequently on the receiving end of Snape's petty comments and straight-out abuse.
Gilderoy Lockhart
Beloved author, Gilderoy Lockart, seemed like a really great wizard, but underneath the saccharine exterior, he truly wasn't. Lockhart was evil, but not in a malicious way, like Voldemort and the Death Eaters. He was more of just an all-around bad person who was only out for himself.
While the Death Eaters had their hidden talents, so did Lockhart. His were finding famous adventurers and using his memory charms to wipe their memories so he could take credit for the things they had done. He even tried to trick Harry and Ron into going into the Chamber of Secrets to their death so he could return saying they tried to rescue Ginny but were unable to due to shock, but he would get credit for killing the Basilisk.
Quirinus Quirrell
One of Harry Potter's first Defense Against the Dark Arts professors was Quirinus Quirrell. He actively searched for Voldemort and believed that the Dark Lord would teach him ways to get people to stop laughing at him, a clear demonstration of the selfishness and evil inside.
When Voldemort took over his body he didn't put up much of a fight, and then ultimately died when trying to kill Harry Potter in the Chamber of Secrets.
Barty Crouch Jr. (AKA Alastor Moody)
Death Eater, Barty Coruch Jr., disguised as Alastor Moody using polyjuice potion, may have seemed like he was helping Harry all along, but everything he did was in the best interest of his final goal of getting him to Voldemort.
Crouch was the one who put Harry's name in the mix of contestants for the Triwizard Cup to let him compete, and he then rigged the game so Harry would be the one win, thus touching the cup which he turned into a port key to where Voldemort was waiting for him. There wasn't anything he did that wasn't evil.
Dolores Umbridge
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.
When she became Headmistress, she ruled with an iron fist and her strict tendencies, which she kept from time with the Ministry of Magic, always held true. Between her treatment of her colleague Professor Trelawney and torturing students during detention, it's no wonder that no one at Hogwarts - save for perhaps Filch and a few Slytherin students - liked her.