Board Thread:Boruto Discussions/@comment-28432164-20160514001744/@comment-1512913-20160514120131

Naruto isn't unbeatable. There's evidence to suggest that:
 * he has lost all of his Truth Seeking Balls
 * he has depleted chakras of the other Tailed Beasts
 * he has gotten rusty

I would say that adult Naruto is actually weaker than 17 years old Naruto. Which leaves him to be:
 * Asura incarnate with Hagoromo boost (although as mentioned lost TSB)
 * Kurama chakra (no evidence of chakras of the other Tailed Beasts still being there)
 * Sage Mode
 * Hashirama cells
 * All nature transformations

And even though that still sounds quite overpowered, Naruto wasn't immortal.

If Naruto is really dead, that means Kurama has been set loose. And I think the most likely reason for Naruto's apparent death is exactly that... Kurama might have gotten extracted.

So the answer to the question: "How to most easily kill Naruto" is simply to take away his belly fox and boy is a goner.