I'm not really a Juvia hater, I just don't like her.
1. She's way too obsessed with Gray
2. Her voice is kind of weird
3. The way she refers to herself in third person is annoying.
4. The way she dresses, although Lucy is worse.
(the pic below is the outfit I dislike most on her... plus her face looks really funny, so I had to share that XD)