how many difficulty levels do you want and what do you want them to be called
this is how i would go , 5 difficulties
Easy as Pie
Normal
Heroic
Real Life
Legendary
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No, real life is actual damage in real life will kill you in the game. Like a head shot will now kill you. A limb shot will wound you, 3 or 4 will kill you. Legendary will be much harder than in Halo