Alois Trancy. People hate him because he's violent and crazy, but that's only because of his childhood. In his childhood, his mother committed suicide, his dad died of sickness, and he was kidnapped, raped, and other bad things. I feel so sorry for him! I almost cried when he died. So, in the end, he's not as bratty as te think!
The only one I can really think of if is Crona from Soul Eater. I don't think anyone really hates it... but I don't really think it is underrated and not liked. o Orochimaru, I think he is sooooo funny... I don't know why.
Most people say he is useless in the Anime which is true but only in the first season and if te read the manga ( since the Anime didn't follow the manga's season 2 ) then te realize that Tskune actually becomes much più powerful and doesn't have to really rely on his harem anymore .
Mizuki Himeji from Baka to Test. I don't understand why so many people hate her, call her a "bitch" and accuse her for being in the way of a pairing coming true when the guy liked her before the other girl showed up. I know everyone has the right to an opinion, but saying such things about her isn't fair.