blackbeard

TLDR: Mihawk is a Marine Hunter who seeks strong swordsmen, and will fight Green Bull because of this (possibly at Impel Down, leading to Weevil and Buggy befriending each other, and Doffy breaking out). Sengoku will fight Blackbeard to save Law, since Rosinante, Sengoku's son, died to save Law...

Luffy's main rival and polar opposite of the D Clan + revenge to capturing Ace Kizaru is light, the polar opposite of Darkness Garp declares an attack on Hachinosu in order to save Koby imho, both Luffy and Koby have to witness Garp going all out and possibly losing to Blackbeard, because...