Hachiman (Nullification Arc)

Hachiman was once a former Kenpachi (possibly the first Kenpachi) and therefore a former Captain of the Eleventh Squad of the Gotei 13 a very long time ago, Hachiman Kenpachi went down fighting against Nullificare however while mortally wounded and surrounded by his squad (who hated him) he was killed by his replacement near the end of the Soul Society-Nullificare War, he was found near death by Eimin who offered Hachiman not only power and a new life but the capacity to continue fighting until the end of time.

Ever since accepting, Hachiman has become a shadow of his truth self having continued to wear much of the morphed armour that he wore as a Gotei 13 Captain but his true form is a Youki-like specter in his rough bodily shape, he is the first Nullificare antagonist to appear in the Nullification Arc and the strongest of those with the Royal Guard-type power level Youki.

Trivia

 * In Japanese myth Hachiman, also known as "Hachiman-shin" or "Yawata no Kami", is the Japanese God of War.