You seem slightly confused. No, they wouldn't be fighting each other, they'd co-operate like they did before because they all despise the Senju. I lol'd at the part where you said Senju could fight for days. Come on, seriously? Yeah well i could say what made Madara a God was his ability to control tailed beasts with his mere 3T sharingan. Just because Hashirama was the best of the best in his clan doesn't mean that the whole clan is really the best; stop generalizing it to others. To be honest, Amaterasu from Itachi would probably solo the whole Senju clan (excluding Hashirama). Hashirama was the only person ever worth of his reputation in his clan. The rest are mere fodders, hence why Tsunade is the only senju alive and the rest are dead. I mean, just look at Tobirama; the weak ass ni*ga who was made a Hokage died to 20 fodder ninjas - probably due to chakra exhaustion. Don't even make me talk about Tsunade. The Senju clan only produced one good Ninja, Hashirama. The Uchiha clan produced a God and a few angels. Madara, Itachi, Obito, Sasuke and Shisui. So you tell me, which clan is the better?
#ThisComingFromASenjuFan.
pffft
Actually they would, example. You and your brother both have MS. Who gets the other's eyes? You're the older Brother and don't want to go blind while your younger brother doesn't want to go blind either so what happens? Fear of going blind you're tempted to take your bothers eyes and also have a fear if you don't that he will. This will create distrust amongst the clan. Some might kill others fearing that they might get killed for their eyes or some might flee in fear that they lack the strength to win.
Hashirama said everyone can see the Uchiha were inferior in their battles (
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) So if only Hashirama was the only thing that made the Senju clan strong then why weren't the Senjus inferior in the fights? Madara and Hashirama would be fighting so other Uchihas and other Senjus were fighting each other so if the Uchiha clan were better without Madara and Hashirama in the picture then the Senju clan would be inferior because the Uchihas would be killing them. Tobirama beat Izuna who was equal to Madara when he was alive. Madara took Izuna eyes after he died from the Fatal wound Tobirama inflicted.Also Madara sees Uzumaki as Senju Linage (who do you think told Zetsu?)
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So Senju/Uzumaki has Hashirama, Tobirama, Tsunade, Mito, Kushina, Nagato, Naruto, Karin. All are strong ninjas while Mito and Kushinas were Jinchuurikis and knew powerful Sealing jutsus while Tsunade and Karin have healing jutsus to heal team. Even Obito said Hashirama and the Senju clan were held as the best clan by many
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You clearly don't know how much chakra is put to control the beast, let alone with Perfect Susanoo layered on top.
But the fact is Madara still needed to use Kurama to try and beat Hashirama meaning he lacked the power to by himself.