This is solely based on opinion.
They are my least favorite characters, especially from when i was reading the books.
1. Dolores Umbridge
If I am writing any articles on least favorite characters then definitely she will make number one. Because I there were times when i felt that she worse than Voldemort himself. She has an annoying crooked smile all the time, even she makes someone cry or suffer. She is like a cyborg with no feelings at all. She makes up all sort of false conclusions like Voldemort never returned and gave Harry a detention full of torture. And she doesn’t give a damn about other's feelings. She teaches the Defence against the arts lessons to students as if it is nothing in near future, And definitely there absolutely nothing attractive about this lady.
2. Bellatrix Lestrange.
If there are any twilight haters out there I know that you see her a lot better than the Bella Swan in the saga. In a way she is because it is quiet visible that this lady is evil. Other Bella on the other hand, she is evil, manipulative and male dependant. Bellatrix is considered more evil and dangerous than Voldemort himself. Torturing is her middle name. Helena Bonham carter’s performance was great and she made Lestrange the kind of person that you wish you could kill. Even though as a character she is my least favourite, she will definitely be one of my most favourite villains of all time.
I am quite surprised that he just made no: 3. Voldemort is defined as an antagonist, who can’t be compared with any others, as he has no hard feelings, a large sense of superiority complex, no loyalty towards his followers and above all, he is an extremely unattractive psychotic prick with no nose (That is not exactly the reason why I hate him). He is a very scary villain. Even the audience fears him as much as the characters.
4. Argus Filch
This guy is nowhere in the dark side, but he is indeed he highly unlikable. With grumpy nature he keeps repelling good people away from him. And he has this annoying temper problems and hatred towards all good wizards. He has a dry sense of humour too.
5. Lucius Malfoy
After reading and seeing the entire franchise, it is indeed concluded that even though he appears bossy and rigid outside, he just as cowardly inside. The cowardly act of Lucius actually makes him a very useless character. At the same time he is also vile and cruel, doing all sorts of harm for the people, like dropping Tom Riddle’s diary in Ginny’s cauldron. At the same time he is a very pathetic and careless person who puts his own family in lot of trouble.
6. Rita Skeeter
Who would want to love a journalist who writes all false things and make sensation out of it? She is in fact a lady who turns herself into a beetle and digs out all dirty secrets and forces the surrounding people to experience. Miranda Richardson is a great actress and did a wonderful job portraying her thus made her like she is in the books.
7. Gilderoy Lockhart
Lockhart, I have to admit that he is a pretty unique character in a way as he is not afraid of showing off in front of a large audience that he is just as dumb witted. He is funny of course, but also he makes money by selling false stories of his. And if anyone knows about his true, he’ll use the only spell that he knows how to use properly, Obliviate. The fact that he don’t care about any others and that he’ll do anything to maintain that status makes him highly unlikable.
8. Peter Pettigrew
Pettigrew is a symbolic representation of a backstabbing type friend. He still talked in a sympathetic, pleading manner to Sirius, Remus and Harry, who already know the full truth about him. His undying loyalty towards lord Voldemort (who himself didn’t deserve finally killed him. Therefore never be good to a person who is bad to everyone.
I initially found him a bit annoying when I first saw the movie Harry Potter and the philosopher’s stone. Then he turned out to be the villain in it. His result was just like Pettigrew’s but two face was actually a beautiful twist.
I have no specific name to add here, but I hate all those death eaters that killed all those poor little children at the end of deathly hallows (they should get the first place of course)