I really want to put Akainu as the strongest, I really do. He's at the center of it all. But I just can't in my right mind until Oda explains how anyone can counter Kizaru fighting at his max potential. He simply created someone too broken and just has him play around or hold back severely to counter act this. We will probably see Akainu go all out, but never Kizaru cause even Oda knows he can't do that.