I swear when I opened this I read it as Kenpachi and couldn't wait to see how that went down.
OT: Kenichi is a much better choice, I'd have to say Kenichi if Miu is there, and idk if she isn't. If Kenichi gets "KO'd" then he'd end up beating Baki on pure instinct as he's done in the manga a couple times now, when he's unconscious his body exploits all the training he's had with none of the hesitation,doubt and fear that he has when he's awake. So, I guess I have to disagree with your initial pick OP, Baki would either have to submit him(hard with all of Akisama's stretching) or KO him so hard he doesn't go into auto killer mode.