Land 1 hit.

Land 25 hits in a single playthrough.

Complete the game on NORMAL difficulty.

Complete the game on INSANE difficulty.

Complete the game on DEMENTED difficulty.

Obtain all upgrades.

Beat the game fast enough.

Go 4 minutes without being spotted. Hiding in closets and safe areas does not count.

Well, did you?

Finish without dying. Don't try reloading a save if you die.

Don't fire a single shot until you have to.