User blog comment:Renkrisb/The Dragneel Brothers/@comment-26416024-20150519215248/@comment-26416024-20150525044400

If Zeref could die easily by conventional means, he wouldn't even need to create E.N.D. He could just get hammered by all the other Etherious demons at once. There has to be something special about E.N.D.'s power.

There are explanations as to why Tartarus did not recognize Natsu. As an Etherious, E.N.D. likely had an Etherious form that changes his appearance significantly and probably spent most of his time in that form.

Obviously this is going nowhere and I'm willing to say that we will simply just have to agree to disagree. Before Chapter 416 confirmed Natsu was E.N.D. I fully believed in the theory that he was E.N.D. and said "I will believe that he is not E.N.D. when I see it". I'm using that again here and will believe he is not evil and the most powerful demon when I see it. I have a lot of hype going into E.N.D. and I'm not going to bring it down until I see that he truly is not what I think he is.