User blog comment:Alexander Dragneel/NATSU EATS E.N.D/@comment-112.209.242.12-20140728133659

Or maybe dude the reason why Igneel can't defeat E.N.D. is because E.N.D. is Natsu himself. There's a bunch of hints that E.N.D. can be Natsu himself. Maybe Natsu is just "asleep" just like Zeref in the Tenrou Island arc.