One Piece: Grand Adventure Cheats :
ReMoval of Opponent's Supports
This is for battles where the CPU starts off with multiple support characters helping them. If you open the disc tray/cover as soon as "FIGHT!" appears on screen, you can battle as normal without their supports interfering. When the battle is finished, you need to close the disc tray/cover to let the game resume.
NOTE: This does not cancel permanent effects, environmental changes, or supports that are summoned during the battle.