Sengoku
Devil Fruit: Hito Hito no Mi, Model: Daibutsu (Human-Human Fruit, Model: Golden Buddha)
Fleet Admiral Sengoku runs the entire Navy from Marie Joie, answering only to the Gorōsei at the top of the World Government hierarchy. He's hard to miss—there's literally a life-size seagull sitting on his hat. He also keeps a pet goat around.
His name references Japan's Sengoku period, the "warring states" era, which fits his role commanding through turbulent times. Sengoku is one of the few people still around who knew the seas during Gold Roger's era, which Whitebeard himself has acknowledged as rare knowledge.
He's best known for controversial calls, particularly authorizing the Buster Call on Ohara twenty years back when he was still an admiral. He handed the Golden Den Den Mushi to Spandine, giving him the power to make that order. More recently, he's shown open disdain for the Shichibukai system, a view he shares with subordinates like Vice Admiral Smoker—though he's stuck with the arrangement regardless.
Content compiled by AnimeList.moe from publicly available sources.