Board Thread:Versus Debates/@comment-25122992-20161209152835/@comment-734582-20170105115026

Ravenlot 27 wrote: Firstly, @Thekillman, I have no idea why do you think that Obito could use Susanoo/PS in this state. When he obtained double MS he could do Susanoo. But we've seen what Susanoo does to your body (just see Sasuke) and when Obito had his double MS, he was already busy dying. Activating Susanoo at that point would almost certainly have killed him (well, earlier anyway).

The other condition (Madara's Rinnegan) is plausible. The same argument applies once more (You don't want to go into war exhausted from Susanoo), but there are also other considerations (rinnegan grants six paths, and he already barely used those), including the time factor (Nagato had 20-ish years to perfect his use of the Paths. Obito had, what, days?) and after-effects. If one-rinnegan one-MS granted him Susanoo, he was in no position to fully use it.

Thirdly, we've seen Obito barely use the Juubi's power, and once more we see reason #2: he barely had time to control it. Obito's entire weakness during the 4th war was that he rushed things.