Sniper Elite: Resistance

This is another one you can cheat at with a manual save, or you can do it the honest way by sneaking your way through the mission. You'll have to get to Hitler without being spotted once, so if the enemy's awareness marker turns yellow, you'll need to reload a save or start again. Using opportunities, like poisoning Hitler's cheese, is a good way to get in and out without being seen.

Alternatively, you can make a manual save before you're about to kill Hitler, reload it, then just kill Hitler without him detecting your presence. At time of writing, this method works.