Kabuto knew that Madara could break out from the edo Tensei

[Lolxe]

On this chapter Kabuto and Itachi have a conversation, back then we couldnt understand what Kabuto was talking about but now its much more clear, read the bottom row and see how after what Kabuto says, Madara shows up, which implies that Kabuto was talking about Madara:

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[Lolxe]

bumping because I uploaded it during the crash and no one saw it.

 

[The Hidden Shinobi]

Hmm it does imply madara. But why would he want madara to return? I guess so he could just get acknowledged from people what he always wanted. But he went toooo far

 

[Minator93]

You are Late U_U

 

[AmaniPaz]

Kabuto is an idiot for bringing him back.