Hashirama is a special case he is the god of shinobi, how can you even compare him to the rest of the army ? Should I remaind you that his summon statue was larger than mountains ? it completely dwarfed Kurama full power...
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Also why are you comparing Kurama's bijuu bomb to the Juubi's ? LOL it's not even close :
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Be realistic, even Obito confessed that they could kill everyone with just one bijju dama, but that Madara wouldn't do it since it would also kill obito (the real plot is why Obito wouldn't use kamui) bottom panel :
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