I liked Kai, Shujinko, Dairou and Darrius! Those 4 are very underrated characters. As for the rest...
Mokap- (The "OW, my balls!" guy? Seriously?)
Jarek- (Forget the fact that he was an obvious clone of Kano, remember that infamous scream of Jarek's in Jax's, Sonya's, and his own MK4 ending?)
Kira- (We already have another evil female character with an ugly face and oversized boobs, we don't need another one.)
Kobra- (Need I say anything?)
Hsu Hao- (Absolutely terrible, worst MK character along with Kira, Mokap and Kobra. And, no, his heart laser thing isn't a saving grace.)
Bo Rai Cho- (As a non-playable mentor and important part to the story, he's cool. As a playable farting fat-ass drunk... what is this, Shrek?)
Hotaru, Taven, Mavado and Daegon should be on the list, too, IMO. I never liked Frost, either, but I suppose she has a fanbase so I won't go down that road. BTW, I voted for Kobra.