Koby is one of the first characters that One Piece fans met, and he is well on his way to becoming one of the series' strongest characters. Koby joined the Marines shortly after meeting Luffy, and he has risen to the rank of Captain. Thanks to Monkey D. Garp's training, Koby has become a powerful melee fighter with advanced Armament Haki. Koby has not eaten a Devil Fruit, which is unfortunate because several Devil Fruit powers would definitely make him stronger.
Source：https://www.cbr.com/one-piece-koby-best-devil-fruits/
