Madara. Dan stated repeatedly no one but Hashirama could stop Madara. On top of that, quantity doesn't work with Madara given the Wood Clone and the fact a bunch of average shinobi together are of no threat to him. If Minato is still the jinchuriki, then Kage.
I think the Kage might have a shot. A-III seemed significantly stronger than his son. Yagura too was presumably better than Mei, considering his hype of being the perfect Jinchuriki alongside Bee. Rasa and Muu seem a bit weaker than their successors. But Minato's speed and sealing techniques should give the Kage some fighting chance, however insignificant.