Unlockable - How to Unlock

CLEAN SLATE - Kill all monsters in level on 'Hurt Me Plenty' or higher.
DESTROYER - Get 100 kills on Xbox Live.
EPISODE FOUR - Complete Episode 4 on 'Hurt Me Plenty' or higher.
EPISODE ONE - Complete Episode 1 on 'Hurt Me Plenty' or higher.
EPISODE THREE - Complete Episode 3 on 'Hurt Me Plenty' or higher.
EPISODE TWO - Complete Episode 2 on 'Hurt Me Plenty' or higher.
HOARDER - Find all items in level.
NEOPHYTE - Complete any level.
NIGHTMARE - Win a Nightmare level in single player.
RAMPAGE - Complete all levels on UltraViolent mode.
ROOKIE - Get 50 kills on Xbox Live.
SCOUT - Find a secret area of a map.