Sniper Elite V2 Remastered

Sniper Elite difficulty is HARD! Luckily if you don't fancy playing through the entire game dealing with bullet drop, more accurate enemies, less health and slower health recharging then there's a way you can cheat this and only have to play the final checkpoint of each level on Sniper Elite difficulty.

Credit goes to HonoraryDecoy and Demon Slayer050 who posted this method for the original release of the game, I just tried it out on the Xbox One Remaster and found it still works.

I'm assuming most people will have already played through the campaign once before attempting this. I'm not sure if it works without having the levels already unlocked.

1: From the main menu go to "Single Player" then "Mission Select" and choose the level you want. I believe they can be done in any order and it will show the difficulty you've beaten each one on down the left hand side. For now choose "Cadet" difficulty.

2: Play through the level as normal until you reach the end, then hit start on your controller and "Exit Game". This takes you back to the main menu.
Note: I usually waited until it triggered the cutscene at the very end of the level before exiting because I wasn't entirely sure in most cases where the level ended. The guides for the 360 version suggest you can wait until the stats screen after the cutscene before exiting but I tried this on a couple of different levels and it didn't work, so I would definitely suggest exiting before then. I'll post more information about the specifics of each level after the method.

3: Go back to "Mission Select", choose the same level you've just played through and this time select "Sniper Elite" difficulty. Let the mission start (I waited until I had control of the character each time) and again hit start on the controller and "Exit Game".

***A couple of people in the comments have said step 4 is unnecessary. I don't want to remove it from the solution completely but feel free to skip straight to step 5 and add in the comments whether or not it still worked for you***

4: This time go to "Single Player" and then "Continue Game". Immediately press the Xbox guide button on your controller and select "Home" from the drop down list. Shut down the game completely (hit start over the icon on the dashboard, scroll down and press "Quit").

5: Reload the game, again go to "Single Player" and "Continue Game". You should notice while you're hovering over "Continue Game" that on the left of the screen it displays the level you've been playing on and shows "Playing As Sniper Elite".

6: If this has all worked correctly then you should be at the final checkpoint of the level but now are playing on Sniper Elite difficulty. Finish off the level and exit back to the main menu after the stats screen. Back on the Mission Select screen it should now display that you've beaten that level on Sniper Elite difficulty.

Level Specifics
Going to post a bit of information about the final checkpoint of each level here. I always waited for the cutscene at the very end before exiting the game but I'm assuming you can exit any time after the final checkpoint activates.

Prologue
I did this whole level on Sniper Elite, it's very short and easy. You only need to snipe the first guy, kill the next 2 in the courtyard, then you can sneak around the large group on the street, go into the building and just run for the objective marker at the end.

Schöneberg Convoy
Destroy the convoy, kill the target and a lot of other soldiers including a tank. The final checkpoint popped up for me here somewhere while I was still up on the vantage point. You need to go back down to the street and search the target guy's corpse. A few more soldiers will appear during this process, should be pretty easy.

Mittelwerk Facility
The final checkpoint here popped up as I came out of the exploding tunnels. There was a sniper in the tower up on the top of the hill where you start the mission and a car appears with about 6 other soldiers. Again, not too difficult if you play cautiously.

Kaiser-Friedrich Museum
This one was more difficult. I got the checkpoint after the big battle on the museum rooftop, once I was heading back down. There are numerous soldiers on the street between you and the exit as well as an enemy sniper on one of the opposite roofs who switches positions between failed attempts. Best to kill them all from a distance while you're still in the building. Then once you've moved down onto the street and through the destroyed building on the right-hand side it will spawn another handful of soldiers and at least 3 or 4 snipers in the buildings at the end of the street and in windows in a building on the right. Take your time and play it very safe with this one, especially with the snipers at the end who can kill you extremely quickly.

Opernplatz
Another difficult one. The last checkpoint here is after meeting Schwaiger and moving back up the upper floor to hold off the assault. Multiple trucks will appear on the other side of the square and tons of soldiers will pour out and start shooting at you while advancing. I tried to snipe as many of them as I could but it's tricky while you're being shot at and they're just about far enough away that you have to account for bullet drop.
The strategy I found most effective was to gather as many land mines and trip wires as possible from the surrounding ammo crates and lay them all in the corridors between the entrance of the building and my position. I then set up and sniped as many enemies as I could. Once the first group got into the building and started setting off the traps I gave up on sniping and moved to the hallway that they would have to come through to reach me. I sat there and shot them as they entered the opposite end until the mission finished.

St. Olibartus Church
This one was much easier. Last checkpoint here popped up after all the sniping from the top of the church, once I'd gotten back down to ground floor. I think there are only 4 more enemies to kill as you leave the church and end the level.

Tiergarten Flak Tower
Also pretty easy. You snipe the target and fight your way back down the tower, then the last checkpoint popped up as I was leaving the building. Again there are only 4 more enemies outside before the end point.

Karlshorst Command Post
This was probably the one I found most difficult. Last checkpoint popped up after killing everybody in the building/bunker and being told to leave. You have to fight your way back through the streets and I think that the level only ends once you've killed all the enemies, most of which are snipers. Some positions seem to be fixed but some definitely move around between attempts. Just take it very very slowly and methodically and try to learn roughly where the snipers spawn. For the most part they only spawn 1 or 2 at a time and don't spawn the next ones until the previous are dead so at least you don't have to deal with being shot from multiple different angles at once.

Kreuzberg Headquarters
The last checkpoint here comes after you've found the map of the launch sites and are being attacked by the elite Russian sniper team. From this position it's only a relatively short run across the rooftops to the exit and it's probably possible to make it but I tried and failed many times. In the end I went very slowly behind cover and killed most of the snipers. They are definitely far enough away that you need to account for significant bullet drop and unlike the previous level it can spawn in 8 of them together and their positions aren't fixed.

Köpenick Launch Site
Oh boy, another level that ends with you holding down a position while tons of enemies come at you. Fortunately the last checkpoint here pops up at the end of the assault, just a few seconds before your objective switches to destroying the rocket. No problem.

Brandenburg Gate
And a nice easy one to finish off the game. The last checkpoint here is once you're on top of the gate so all you have to do is snipe the target. Not quite as easy as it could be as he's moving quickly, far enough away that bullet drop factors in, and there are lots of things obscuring your vision but I think by this point you shouldn't have any trouble with it.

This is not a solution but a heads up. Even though they brought the feature to play the entire campaign in coop, the achievement doesn't unlock if you complete the campaign on sniper elite difficulty while playing coop. It must be done single player.
I had to find out this the hard way with a friend after completing the campaign in coop.