User blog comment:Miskos3/Fairy Tail 520: Dragon or Demon, Review/@comment-5303512-20170204123939/@comment-175.145.234.92-20170204150558

Actually seeing this chapter i think i understand when Zeref said who will reach him Natsu or END, i think he meant these two possible scenarios. Natsu could either

A. choose to accept his Demon Powers and kill Zeref as an Etherious and Zeref's ultimate creation.

or

B. reject his Demon Powers and choose to face Zeref as a human and Zeref's brother.

Natsu chose the latter which Igneel says is the right decision cause now Natsu isn't bind to Zeref anymore.