Jack

Jack used to be a really well renowned ship captain for the king's guard. One day when he was out on patrols, a pirate ship caught him and his crew off guard and slaughtered everyone except Jack. They forced him to work on the pirate ship with them as a someone to clean the deck and do whatever gross shitty jobs they wanted him to. However he was incredibly charismatic and slowly worked his way up in favor and eventually became first mate. But every night he would look off into the ocean and just dream about killing every single one of the pirates; finally getting revenge for his fallen crew. And then, one night, he heard the ocean speak back to him. It was a few weeks before he could finally understand what it was saying and when he did, he agreed to a pact with it immediately and slaughtered every single pirate on the ship with the Fathomless's power.