Zeref may have gained Fairy heart but he may have lost his immortality. He was cursed for dabbling with life and death, which he did to bring Natsu back. He has now killed Natsu with his own hands. Which may have removed the curse... it could be like Voldemort and horcrux. Whatever happens...
It was great seeing Zeref use fairy heart, I really don't see Acnologia besting Zeref now. The only disappointment is that Natsu would have demolished base Zeref, He was certain that the flame would erase Zeref, and he knows best because he almost killed Zeref in their previous battle so he...
