I believe I suggested Baku, my Missing Ninja from Sand as a potential member of the Despair Squad.

He doesn't have a personal stake in the Hope Generation or the Sound Village per se, but he does work as a mercenary and have a frothing irrational hatred of child prodigies and work for basically anyone who can pay him.

Attacking a group of highly praised children who are competing for their village's spot in the Chunin Exams? He'd do it for free if he heard.

Honestly, if Kimiko needs a specific fight for just her he can do it.