I'm adding my Crysis 3 walkthrough on Xbox 360, but the site says it's been reported the game doesn't have a difficulty level setting. This is wrong, it does have difficulty settings.
I'm not sure of them all but they do have Veteran and SuperSoldier. With SuperSoldier being the hardest. However, the game does have a glitch where some people (myself included) do not get the SuperSoldier achievement at the end, even though it is completed on that difficulty.