User blog comment:IamJakuhoRaikoben/Chapter 413: The Book of E.N.D, Review./@comment-83.253.84.32-20141222153307/@comment-7418318-20141223122857

But even in F-Rogue's future is was "only" 90 % of mankind he killed. And he obviously didn't destroy the ruins of Mercurius thoroghly enough to also smash the Eclipse Gate.

With a breath attack that can level entire mountains and scour islands down to the bedrock, I think he just got bored of wiping out Humans rather than being unable to complete the genocide.

10 % might not sound much at first, but when you take the entirety of mankind as a base, 10 % is still quite a lot. Certainly much more than a few scattered survivors or stragglers.