User blog comment:GotMilk5101520/How will the Tartarus Arc Part 4 will end?/@comment-5303512-20140709034950/@comment-1776824-20140709045332

Igneel chose not to kill E.N.D. It was made quite apparent by the tellings of Atlas Flame and Zeref that he could have and had every capability of doing so, but just outright decided not to for reasons unknown.