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Playstation 2 - Killer 7 cheats

Unlock Killer 8 mode and Young Harman as playable character:
Finish the game in normal or hard mode.

Unlock Hopper 7 mode:
Finish the game in Killer 8 mode. 

Watch different ending:
Finish the Killer 8 mode. 

Killer 8: 100 Serum Vials:
Go to the "Press Start" screen and enter 
Down, R1, Up, L1, Square, X, Triangle, Triangle
After you entered, you will hear a sound.
To get another 100 vials, replay the code enabled level.