Worstgen

Mihawk and Shanks are noted to have had once a legendary rivalry similar to Roger and Whitebeard's rivalry and that led to many battles so great that even Whitebeard acknowledged their epicness, right until Shanks lost his arm which led Mihawk and him to bury the hatchet.

What were the reasons of that great rivalry ? What may have caused these two then very promising rookies to developp such a feud with each other ?