Ace's tattoo in One Piece holds significant meaning. The tattoo on his back is a symbol of his pride and joy, representing his allegiance to Whitebeard, whom he viewed as a father figure. Additionally, Ace has another tattoo on his upper left bicep that spells 'ASCE' vertically. The 'S' crossed out is a tribute to Sabo, indicating his jolly roger. This tattoo is a symbol of the bond between Ace, Luffy, and Sabo.