I think it's been implied numerous times that Natsu is end. And END stands for Etherious Natsu Dragneel according to fairy tail wiki. Since when was it confirmed that Natsu was END? I'm up to date on the manga and even though it's implied, that doesn't mean he's END. Or am I sorta forgetting something? I do somewhat remember Zeref saying Natsu was end or at least implying it. But if he's end and igneel knew who end was, why would he tell Natsu that he is the only one who can defeat end?