User blog comment:B214/Chapter 503: The Last Sight Seen/@comment-5303512-20160926122648/@comment-5303512-20160928173204

@Wrath; And yet other Etherious like Deliora and Lullaby have been around for 400 years too, while one is still animalistic, he doesn't show signs of killing Zeref, while the other one is clearly intelligent, and the same doesn't show signs of killing Zeref either, not all demons are in the same boat behavioral wise. Plus we don't know if Natsu awakened as END for the first time.

@B214; well, even so, it is not to say that he isn't fully there mentally either.