A few very important points:
1. Hahirama fought Madara alone not the Kyubi, Mito helped him and im pretty sure Madara didnt have his space time back then, he didnt have senju DNA and he wasnt a creepy immortal(ish) zombie + it was all a part of his plan
2. lets say Hahirama were facing an opponent as strong as the Kyubi i.e. that means he couldnt tame him with his wood, tell me what the f?ck can wood (his by far most memorable ability) against such power, no srsly you think a forest will stop the power of the Kyubi?
3. When Minato fought Madara he Rasenganed the crap out of him and Madara retreated, why? cuz he didnt wanna die, if he just wanted to get away than why the hell would he even attempt to fight Minato (you say because he wanted him to distract him from the fox, I say he knew Minatos abilities pretty well and if he didnt consider the possibility oh him teleporting back to the village ... well than our Tobi really isnt all that bright)
4. the 3rd was desperately waiting for Minato during the fox attack even though he had a batallion of Konohas greatest ninjas at his side
5. Minato defeated Madara, saved Kushina, saved his son, summoned Gamabunta, released Kyubi from Madaras control, teleported a tbb, teleported the Kyubi!, sealed the Kyubi with what are so far the most complex sealing techniques in the Narutoverse (and he did two fuinjutsu at once) and at the same time thought for about 20 years ahead, ...
6. to top the previous fact he was under stress even when Kushina was in labour, consider what psychological trauma he went trough after Madara attempted to blow up his newborn son and consider that he was thinking that his wife Kushina could die at any moment (because the jinchuurikis usually die after the TB extraction) and to top it th Kyubi was raging in Konoha and noone could stop it and as a Hokage the entire village is his family (imagine what stress that is, you cant function normally in such times, no human can and if you say that is a weakness I say you are weird)
7. last but not least he was able to put up a barrier so strong not even Hiruzen could enter while fighting the Kyubi
8. Hiruzens last resort VS the First Second and Orochimaru! was Minatos tech, and he seemed a lot more scared of Minato than all the other 3 put together
