Sniper Elite: Resistance

I as able to do this in 3 minutes with this simple method, the only prerequisite is that you unlock the “vittoria’s view” starting location which is located on the north eastern part of the map (top right most area).

When you unlock this area select it as your spawn and start it up on authentic difficulty.

Walk down the Main Street right in front of you when you spawn in. There are no enemies on this street until the very end which is where there will be one enemy.
You can either kill him or sneak past him. There will also be a vehicle driving by here just make sure you wait it out before proceeding slightly to the right of the road the vehicle was driving down.
Proceed past the white tent and through the open doors. There are a couple enemies around here but in my experience they were too far away to bother me as long as you’re sneaking most of the way.

Now you’ve basically reached hitler once you pass the truck in front of you, you will see him talking to another officer assuming you’ve made it to this point fairly hastily because hitler will move on if you take too long.

Hide behind the boxes that are nearby the stairs and wait for their conversation to finish. Watch out for the guard that pokes around while you’re waiting just stay behind the boxes.

Hitler will begin moving towards you and once he’s right by the boxes make your move and press Y to kill him with a takedown.

At this point retrace your steps the way you came the only worry you should have is the vehicle from earlier but it should be somewhere else, and the guard that you either snuck by or killed when we began.