9x17 - Fairy Tail

With Alvarez's vanguard defeated and Brandish imprisoned, the guilds of Fiore hold back the advancing armies. Mavis sends several members to reinforce their allies in the northern and southern fronts, while the Four Emperors of Ishgar defend the eastern side. Suddenly, the guild detects Natsu flying with Happy towards the western army led by Zeref to defeat them by himself. After drawing Zeref out by defeating several hundred soldiers, Natsu overpowers him with his ultimate technique, Fire Dragon King Mode, a temporary reserve of magic power left behind by Igneel. Convinced that Natsu has found the means of killing him, Zeref thanks him and several others as he awaits his death.