Navin
MALDREAD
Man you really hate here huh? Can you give me a reason how to hate someone who has a hard-to-hate character?
Serena was close to being an outright Sue (she would have been if she defeated Elle) at one point. Even if they have likeable personalities, it's understandable why some people don't enjoy those type of characters.
I don't think it helps that her goal was something like a Best Waifu Kalos contest, which combined with her comment that "girls should always attend to their appearance and make themselves cute" + pointless ship pandering, kind of leaves the wrong impression even if she doesn't act unlikeable per say.