Originally Posted by Eighty6ed
OK. Madara is the obvious choice for a TON of reasons. No real need to go on listing them as its been said already time and time again. Primarily being the ongoing speculation that Tobi isnt actually Madara. Tobi needs Madara's identity to maintain his credibility with Sasuke.
The 1st Hokage. Yes, his soul should be sealed in the Shinigami but we dont know to what extent Kabuto has improved the resurrection jutsu. Maybe its now possible. Why would it scare Tobi? I think thats pretty obvious. He's been beaten before and could reveal Tobi to be an imposter.
The 4th Hokage. Again, above explanation as to the Shinigami. Yet another guy that could put a hurtin on Tobi and possibly reveal him as an imposter.
Rikudou Sage. This one to me seems a longshot, but still intriquing. Would definately put Kabuto in the madman category to summon someone who, above anyone else, have the potential to beat the control of the jutsu that Kabuto has, and thus turn on him. Plus, RS given the opportunity, would almost without a doubt completely unravel all of Tobi's plans single handedly. I don't really seeing Edo Tensei having the potential to resurrect and essentially duplicate Rikkudo Sage with the Juubi.
Madara's brother. Assuming that Tobi actually IS Madara, who else has the potential to change Madara's mind more than his brother. What would Madara do if confronted by his brother? Who the hell knows?
Anyone else? I just really dont know. Haven't seen any candidates that would really frighten Tobi the way he was IMO.
to the bold and under lined above... i believe the conclusion has been drawn that Edo Tensei brings a person back at their peak (dont read the databooks but from what i've read in this forum it's a "fact"). thus it's not up to you to believe it, it's up to you to know