There is no official "all cards unlocker" or built-in cheat code for this game. Konami did not release a universal unlock feature. The game was designed so you unlock cards progressively by dueling opponents and meeting specific conditions (e.g., defeating certain characters, achieving high scores, or performing special moves like Exodia or Final Countdown).
For the purist, grinding for months against Kaiba is a rite of passage. For the collector, the deck builder, or the nostalgic adult revisiting their childhood, the unlocker is a key to a lost world. It turns the game from a chore simulator into a sandbox of vintage Yu-Gi-Oh! strategy. yugioh power of chaos the legend reborn all cards unlocker