Dunno really, why he's considered the strongest. As you say, Kidoumaru appears stronger because he was fighting Neji and shit. But then again, Sakon has barely been injured by Kiba, while Neji killed Kido off. And Kido played cheap on distance, too.

Kiba owns.
And fuck YES did the music NOT fit to the flashback. I was like "what kind of damn flashback music is THIS?"