Remus Moony J Lupin
I hate Peter Pettigrew, Dolores Umbridge, the Malfoys, Bellatrix, Greyback, and Cornelius Fudge. Quite a few of those people have a special degree of loathing attached to them because of things they did to characters I like.
And since I am counting hatred based on offenses against my favorite characters, I'll add Dolohov to that list too.
I see a lot of Ginny hate here, but I have a hard time seeing why. I mean, her attitude toward Fleur was a bit annoying, but I tend to think that Veela bring that out in women almost as much as they bring out the lustful side in men.
Um...it's because she is a boring, flat, barely two-dimensional fangirl whose "character" we are supposed to adore, yet other characters who act the way she does get bashed and crucified. For instance, we are supposed to see Cho as unreasonable when she gets jealous of Hermione, but Ginny being jealous of little Gabrielle is supposed to be "cute" and shows us how much she "loves" Harry. Or, Zacharias Smith is a douchebag for badmouthing Harry, but Ginny can say as many nasty and rude things as she wants to Ron or Hermione, but that doesn't make her a b***h, it just makes her "spunky." Rowling certainly didn't hold back on the double standards with Ginny, and the fact that the Gin-Bot was shoved down everyone's throats to the point of suffocation didn't win her any points in my book, either. Ginny is only there because Rowling wanted Harry to marry into the Weasleys, which makes me believe that she wrote this pairing merely to fulfill some weird romantic fantasy. Sort of like Bella Swan's role in the Twilight books, but at least Stephanie Meyer had the cajones to actually admit it.
One character I started out liking but ended up hating was Tonks. IMO, the relationship with Remus ruined any potential she had as a character. Remus/Tonks made even less sense than Harry/Ginny, not to mention that Rowling completely pulled this pairing out of her a**--but then, she did that with a lot of things in the last two books. In HBP Tonks was a whining, pathetic mess, and in DH, she gave birth to Teddy and got killed. Ugh, it ticks me off.
I also don't like Molly. I think she's overbearing and can be quite rude, and always has to stick her nose into everyone else's business. She is the last person I would want as a mother-in-law.
I don't like Snape because he bullies children, any decent school would fire a teacher for treating students the way he does. Same with Umbridge. I don't care for Dumbledore because he left Harry to be abused by the Dursleys, and I really don't care how anyone wants to justify it, child abuse is chiild abuse.