How to unlock all secret cheats
How to unlock all secrets (cheats)
Defeat the Warlord on Chapter 4 (Hard Difficulty)
Invincibility
Defeat Oblivion on Chapter 5 (Hard Difficulty)
All Weapons
Defeat Oblivion on Chapter 5 (Any Difficulty)
All Character Weapons
Defeat Oblivion on Chapter 5 (Hard Difficulty)
Infinite Ammo
Defeat Alpha Fireborn on Chapter 4 (Hard Difficulty)
All Keys
Defeat Oblivion on Chapter 5 (Any Difficulty)
Big Heads
Defeat the Oblivion Gunship on Chapter 1 (Any)
Headless
Defeat The Xiphias on Chapter 2 (Any Difficulty)
Shorty
Defeat The Xiphias on Chapter 2 (Any Difficulty)
Skinny
Defeat the Opisthor on Chapter 3 (Any Difficulty)
Big Hands & Feet
Defeat the Oblivion Gunship on Chapter 1 (Any Difficulty)
Thanks to Solaire of Astora for their excellent guide; all credit belongs to their effort. If this guide helps you, please support and rate it here. Enjoy the game.
Finally got all the cheats unlocked.