Go to multiplayer with a friend. Have one of you do a bane move on any enemy. Then the other shoot the enemy who's being killed with the long range attack. If the shooter kills the enemy before the bane move is over, both players will gain experience from the kill!
While you are playing pause the game, then hold the R and L buttons, then type the code for the character you want to increase.
Reduce your ranged attack meter to 10, and hold Y to charge up a devastating attack right before an in-level cutscene occurs. When it is over, you can use your devastating attack over and over again(if you use a ranged attack, the effect stops).
Complete the listed objectives to unlock the secret characters.
Pause the game, hold L + R and enter the following (some codes can only be activated after completing the game once):