Is it normal to hate someone for no reason?
Yes, it can happen to feel intense dislike for someone without knowing why. Usually there’s some trigger you haven’t put your finger on—or “hate” is a big word for a strong, unexplained dislike.
You might be reacting to their mannerisms, a bad first impression, or something they remind you of without realizing it. Sometimes you’re stressed or in a bad mood, and one person just becomes the easiest target for that feeling. Lots of people have an inexplicable “I just don’t like them” reaction now and then.
The feeling itself doesn’t make you a bad person; what matters is how you treat them. You can keep things polite and give yourself a little time to figure out whether there’s a real reason—or whether you simply don’t click. If the feeling is taking up a lot of your attention, it may help to ask what it brings up for you.