User blog comment:Xilinoc/Ch. 573 (Let Unohana return plz)/@comment-3290324-20140319212559/@comment-1268838-20140319213237

Well, it's been pretty well established that having more reiatsu than someone pretty much renders their abilities moot. On top of that, this is not even the first time that Kenpachi has cut someone who is supposedly uncuttable.