When it comes to the adults of the wizarding world of Harry Potter, many are just as bad as the children, if not worse. It's amazing how the Ministry of Magic expects teen witches and wizards to behave with decorum at all times, threatening them with expulsion for accidental magic when many of the adults carry out heinous deeds and get away with it every day.
It's one of the many ways that Rowling has created a rich, layered world that feels so real, even if it does annoy, and even harm, the children of the magical world. Here are some of the worst adults in the series, along with the various misdeeds that see them labeled as such.
Remus Lupin
Everyone thinks that Remus Lupin is one of the kindest, most caring teachers at Hogwarts School of Witchcraft and Wizardry, but in reality, he's got some major problems. For starters, he forgot to take his wolfsbane potion and nearly offed his best friend's son and his friends during a full moon, which is completely irresponsible.
Later, he left his new family claiming it was to protect them, when they needed him more than ever. He also sought out Harry during this time, wanting to work with him instead, and when Harry called him out he was actually cruel to the boy.
Gilderoy Lockhart
The former Defense Against the Dark Arts teacher traveled the world, erasing famous witches and wizards' memories and claiming he was responsible for the great deeds they had performed. Dumbledore had to have known the man was a liar, but he hired him anyway.
Lockhart was vain, irresponsible and downright cowardly, and his willingness to totally mess up any other life in order to further his own personal agenda made him especially horrible.
Sybill Trelawney
It's bad enough that Dumbledore hires the most dubious people as faculty members of Hogwarts (leaving us to question why people like Molly Weasley aren't teaching), but he even hires people that he knows to be frauds. Surely he knows this is providing the Hogwarts kids with severely lacking educations?
Trelawney is an example of this gross oversight, but she's also worse because she routinely gives the students anxiety with foreboding fortunes that predict their deaths. With everything the students already have to worry about, having her around only worsens the Hogwarts experience.
Rubeus Hagrid
As endearing as Rebeus Hagrid is, he's also a danger to have around children. Aside from the fact that everyone is still wondering why Hogwarts even needs a Keeper of the Keys or gamekeeper (Dumbledore seems to just want to give misfits a place in the world), it is downright irresponsible to hire Hagrid as a Hogwarts teacher. He gets students injured during almost every class and is a lawsuit waiting to happen.
Hagrid smuggled a dragon's egg into Hogwarts at one point. Even Dungeons & Dragons newbs know how idiotic this would be, and Hagrid, a half-giant, has already had enough experiences with dangerous creatures to know how much of a risk it presents. It's the very reason he was kicked out in the first place. He also brings a giant to the Forbidden Forest, further endangering the kids, and asks his favorite students to take care of him!
The Entire Ministry Of Magic
How creepy is it that the Ministry of Magic sees you when you're sleeping and knows when you're awake? It's like a giant, demented version of Santa Claus, that randomly punishes kids, expelling them when they accidentally use magic. Every Minister of Magic prior to Kingsley Shacklebolt has also either been a daft coward or a swaggering jerk. All of them thought they could use Harry Potter for their own personal gain.
An organization that employs someone like Dolores Umbridge and allows her methods of "teaching" and bigotry is bound to be a nefarious one. When the Ministry becomes even more corrupt as the Death Eaters take over the place from within, it's not even that big of a surprise.
Lucius Malfoy
Obviously Voldemort and the rest of the Death Eaters were the worst of the worst, but Lucius Malfoy deserves a mention as being one of the worst parents of the wizarding world. He's a terrible father to his own son, raising him to be a narcissistic little bully, but he even goes as far as bullying the kids at Hogwarts himself.
It's pretty bad when you're so insecure and full of hate for Muggle-born wizards that you take to bullying people like Hermione Granger, Harry Potter and other students. Most of these instances didn't even have a thing to do with Voldemort's orders; they were just things he did to pass the time.
Albus Dumbledore
"Machiavellian sociopath" might be a slightly harsh way to describe Albus Dumbledore... but is it really? He has known that Harry has to sacrifice himself all along and he's totally okay with it, grooming the boy as a lamb to slaughter (in Snape's words). He does this with many people in his life, using them for his own grand plan, and even if he has good intentions, it doesn't make it okay.
He sends Harry on dangerous missions, hires terrible or dangerous teachers, casts a spell to render Harry immobile, powerless as he watches Dumbledore bite the dust in front of him and may have even accidentally offed his own sister. He was also in love with Grindelwald, who he allowed to literally get away with murder until he finally took action against him.
Argus Filch
The fact that Hogwarts even requires a person like Filch to be a janitor is ridiculous. Magic would make it so every task the caretaker has to complete over in seconds, and it would also be a great learning experience to have the houses have to complete magical chores (or even manual ones since there's no physical education at the school). To hire Argus Filch of all people, however, makes it even worse.
This resentful squib is the only member of the Hogwarts faculty and staff who is pleased to have Umbridge at school. He longs for a day when he can physically harm the students he loathes, and he doesn't hide it at all.
Severus Snape
Yes, Snape gave up his entire life to work as a spy for the Order of the Phoenix, and we have no idea what that entailed leading up to Voldemort's return. That doesn't excuse all of the times he was such a bully to his students that one of them, Neville Longbottom, was so terrified of him that his boggart turned into Snape, indicating that his Potions professor was his worst nightmare.
Snape routinely bullied not only Gryffindor students but any Hogwarts children who weren't in his own Slytherin House. He took points away for random things, embarrassed students on purpose and generally took out his entire childhood experience on the kids of Hogwarts.
Dolores Umbridge
While the Ministry of Magic is bad enough, Dolores Umbridge deserves her own entry as the witch everyone hates even more than Lord Voldemort. Umbridge is a bigoted, evil woman who enjoys punishing her students with tasks that physically torture them. She takes great pleasure in restricting students, exercising authority over other teachers and abusing her power any chance she gets.
The fact that Umbridge survived the Second Wizarding War is a great affront to many fans. She was a cruel sadist who not only had fun tormenting adults and children alike, but dressed it up so it appeared to be wholesome.