There are two ways to unlock sudden death. 1. You can beat winback on hard or2.
You can use this cheat l2 r2 l2 r2 o triangle o triangle hold l1 and press start

To get Max power mode:

At the "Press Start" screen quickly press L1,R2,L2,R2,L2,Triangle,Circle,Triangle,Circle, then hold L1 and press start to unlock maxpower.

If you did it corectly you will hear the sound of a gunshot this mode allows you to start of with all wepons and infinite ammunition.

Note: The code must be entered before demonstration mode begins....!