Happosai I totally agree with, he was so bad that I stopped reading the manga for about six months after he got introduced. Genma was also pretty one-note, but he at least has his moments.
But Akane? Come on, mate.
Also, if a continuation is ever done, I demand 1000% more Ukyo, because she was horribly underused and a shine better than Shampoo (so fucking obnoxious),