Originally posted by another user
1.) Unlock Combat Arena, by beating the story once and then clearing the Challenges of Olympus mode.
2.) In the Combat Arena option screen, set Kratos’ Health to “Level 1” and difficulty to “Titan.” Set up the Enemies option with creatures that can kill you quickly and start the battle.
3.) In the Combat Arena, die five times in a row and the game will prompt you to switch to Easy mode. Select “No” to exit to the main menu.
4.) You should hear two different music tracks playing over each other. Furthermore, the "Maxed Out!" trophy will be unlocked if you didn’t already have it. From the main menu, select “New Game” and the difficulty of your choice to activate the glitch.
No words yet on when Santa Monica Studios, the publisher, will release a patch for the glitch or even if they will at all!