Monkey D. Garp

Monkey D. Garp is a Marine vice admiral in the One Piece series. He is Luffy's grandfather and Ace's adoptive grandfather. After the war, he became the vice admiral who trains new Marine recruits such as Coby. Garp is one of the major active figures, along with Sengoku, Shiki, and Whitebeard, who saw the "King of the Pirates" when he was alive.