There are many characters in books who DESERVE our unbridled hatred. For instance, I don’t think you’ll find a single person who is like “I get it, Dolores Umbridge had her flaws, but don’t we all?”
However, there are also many characters we hate for no real reason. Look, I’m not here to change your minds about those people. I’m sure I hate many of them as fervently and inexplicably as you do. It’s just that sometimes it’s worth taking a step back and asking yourself, “But why? Why do I hate this character?” Sure, your brain will probably go “THERE IS NO WHY, THERE IS ONLY THE HATE,” prompting you to continue down a dark and sinister path from which there is no return, but here are some of those characters anyway.