People really think Minato is Kabuto's trump card? No. We have CLEAR explanations as to why that's not true. Kabuto mentions, several chapters after he shows Madara the final coffin, that "none of the previous Hokage can be summoned" because at least part, if not all, of all their souls have been sealed somewhere other than the "pure world" from which souls are called back by Edo Tensei (1st, 2nd, and 3rd were fully sealed by Reaper while 4th sealed half his soul in the Reaper). But, Minato WAS Orochimaru's final coffin... kabuto specifically says that Orochimaru tried to summon the 4th Hokage but failed cuz part of the 4th's soul was sealed by the reaper... so i hope no one is still confused about Minato in regards to Edo Tensei