4. Dudley, Petunia, and Vernon Dursley
Dudley, Petunia, and Vernon deserve a place on the list of the most disliked characters in the Harry Potter series, individually. As a family, though, they're truly one of the worst. Apart from any of the three disliked characters ranked above them on this list, Harry couldn't have lived with worse people. They truly hated who he was and what he represented. And, they abused him for years. He lived under the stairs with the spiders while Dudley had a bedroom and a room for all of his toys!
For four books, the Dursleys make Harry's life a living hell. It's not enough that he lost his parents and has to live with them, but they resent him for just existing. It's truly cruel. Harry has no memory of his parents because they were murdered, and the Dursleys are like, "Ugh, he's so annoying with his presence, aura, existence, and messy hair."
Like you expect Harry's enemies to be high on this list, but you don't expect his family and the people he lived with for 11 full years to be the cause of so many issues in his life.
There's nothing likable about Dudley, Petunia, or Vernon, to me. I don't agree with how Rowling portrayed the Dursleys, specifically their physical appearance. Their actions clearly show the type of people they are, especially in the first book with how we meet Harry, how he's punished for nothing, and how they literally run to an island to escape Harry making something of his life.
The Dursleys are gross, and I hated how there was some level of redemption given to them during the scene in which the Dursleys leave Privet Drive because Voldemort and the Death Eaters will attack when the Bond of Blood Charm breaks.