What can Minato do to kill them? Again, my rasengan post above, and I hope you're not going to suggest he'll stab them with a kunai. In reality, Nagato isn't stupid enough to let paths be drawn apart when facing an opponent of Minato's caliber, and shared vision will help a lot because when Minato tries to FTG behind them and rasengan, they may be able to dodge, much like Asura+Deva against Kakashi's chidori, and, let's not forget, he is dealing with more than one path. When trying to attack one path, he is prone to attacks from others, as he cannot defend himself whilst trying to (presumably) rasengan another path.