Old players maybe remember that the crysis multiplayer was the most cheated game in its era. It was totally unplayable due to all the cheating and that killed the game.

One way to make cheats. You could load up the SDK in visual studio. Find the code that's removing -1 ammo when shooting and edit it to not do that (most of the physics and game logic was editable that way). Compile the DLL. Replace the original DLL in the game directory.