Ah, how to fight 6 paths Naruto. There are two good ways to beat him. Make sure he never uses his mystery or use a mirror and healing lineup. 6 paths strength comes from his ability to heal for 25% every time he uses his mystery. I've seen nearly dead 6 paths go back to full hp in Gnw. It's honestly disgusting.

So, how can you make him never use a mystery? Well, luckily there is a brand new ninja that can do both of the two ways to stop his mystery, Undodgable interrupt and increase mystery cool down, in other words, 4 star your shizuka. I honest laugh every time a 6 paths Naruto gets his mystery increased by 2 when my shizuka and gakido chase hits. Granted, the interrupt requires the 6 paths to be less than 30 Chakra, but for a free ninja, shizuka is pretty * amazing. Edo minato is also very good as well as Kakashi susanoo. If you have trouble going through those shields, madara 5 kage is good but Han is still a decent alternative as he also has super armor and an auto attack dodge. Stealing Chakra is another good way to pair with edo minato as it completely stops a 6 paths if you have initiative.

2nd way, mirror. So if you cant stop him, use edo itachi, kurenai, or ningenedo. A lot of 6 paths strength comes from making one of your ninjas continuously immobiled. Use mirror to make sure that doesn't happen.

3rd way, just get a crap load of power and do the opposite of p1 stacking, make sure your other ninjas don't die to the first few 6 paths mysteries.

So game knowledge is p2w now I guess¯\_(ツ)_/¯