Board Thread:Versus Debates/@comment-25122992-20170212172849/@comment-1872728-20170213192503

If Obito can summon the Demonic Statue of the Outer Path, absorbing his Six Paths of Pain along with Kinkaku and Ginkaku to turn into the Ten Tails, and Obito becoming the jinchuriki, he'll be the strongest, then Madara will be the second strongest, and Kabuto will be the third strongest with Nagato, Itachi, and A (top three strongest).

If not, then Madara is the strongest, Obito and Kabuto could go either way to be honest.