Rear Admiral

In One Piece "Rear Admiral" is a marine officer rank above Commodore and below Vice Admiral. It is the first (the lowest) admiral rank.

So far the only person seen in One Piece to have held the rank of Rear Admiral is former marine and current pirate X. Drake and an unknown Rear Admiral who was in command of the battleships of Impel Down when they were after the Jailbreak League's battleship.