Hmm..from what you've said you like/dont like, I would definitely check out:
TaeYeon (from SoNyeoShiDae/Girls Generation) - She has two solo songs "If" and "Can You Hear Me"
and people have already mentioned Cheon Sang Ji Hee (CSJH)
Dj Badtz definitely knows her stuff , if you really like ballads like i do, then you should totally check out Younha and TaeYeon. Younha has a powerful but at the same time, beautiful voice and her music ranges from ballads to rock. Go can't go wrong with Younha.
You can also try out Davichi, their newest min-album is <33.