To Get all caracters:
Hold Start, O and square at the same time.
During the battle, when you have a fireball like aura surrounding you, go up to the person your fighting, and keep pressing O. Sooner or later they will run away to charge up which wastes energy. Keep after them and continue doing this until they run out of energy. Hit them a couple of times, then recharge. Go up to them and keep on pressing Up + O at the same time, and you'll win.
Raise Ending Level to 999%:
After a battle ends, you will go to the save/continue screen. Hold Select and press TRIANGLE, SQUARE, and X for 5 seconds then release. Now use up and down to scroll between scores.
Play as Super Sayin:
When you fight with Frieza use Krilin. Let Frieza kill Krilin and then you will be able to play with Super Saiyan Goku.
Thanks to Revolution readers Victor Gregorio Rodr'guez and Ryan!