Hex Cheats:
Use notepad or a text editor to edit the autoexec.cfg file

Change the following

Invincibility

Change "PlayerTakeDamage" "1" to "PlayerTakeDamage" "0"

Enemy Invincible

Change "AITakeDamage" "1" to "AITakeDamage" "0"

No Clipping Mode

Change "PlayerClip" "0" to "PlayerClip" "1"

Enemy takes ALOT of damage

Change "AITakeDamage" "1" to "AITakeDamage" "99"