you should read manga, that was filler
in vs hiruzen he didnt show anything so special
the only way he beat madara and stole his kyuubi, is that he used his own tailed beasts he collected...(as tobi said), yamato also said that hashirama was made hokage because his ability to control jinchuurikis and tailed beasts...so thats the way why he is considered on so6p level, the tailed beasts...
which part?
the part where he can use bringer of darkness which is the best genjutsu against the uchiha's sharingan?
or
whether the frist has good taijutsu?
and he does have good sealing jutsu, yamato supressed naruto 4 tail mode with one of his seals.
also hasihrama clearly at this point mentioned he didnt use tailed beasts against him. Madara would have mentioned that my madara fan friend.
When Madara was talking about Hashirama's abilities he would have mentioned he used multiple tailed beasts against him. There's no reason for Madara to hold back on the truth like that, it would only make him look A LOT weaker compared to Hashirama. The whole reason he wanted to go against the leaf village was to prove to the world the Uchiha were equals with the Senju(As Hashirama was chosen to be Hokage) and by lying like that it would stand against his principles and beliefs back then. Madara also said Hashirama was the only person he admired, so by saying Hashirama simply used multiple bujjs to defeat him would take away from Hashirama's stature as a shinobi. So basically he could have just have easily said Hashirama used multiple tailed beasts and no one would known the truth anyway. But he didn't.