Complete any level
Get 100 kills on Xbox Live
Find a secret area of a map
Find all items in level
Kill all monsters in level on 'Hurt Me Plenty' or higher
Complete Episode 1 on 'Hurt Me Plenty' or higher
Complete Episode 2 on 'Hurt Me Plenty' or higher
Complete Episode 3 on 'Hurt Me Plenty' or higher
Complete Episode 4 on 'Hurt Me Plenty' or higher
Complete all levels on UltraViolent mode
Win a Nightmare level in single player
Get 50 kills on Xbox Live