Sniper: Ghost Warrior

This is totally doable on a first playthrough, and IMO, the only rewarding way to play this game.

Conserve your health packs. During some scripted moments, you'll have to run for your life from a swarm of enemies, and the only thing that will keep you alive is a good supply of these. So try not to use them when fighting small numbers of isolated enemies, or shortly after a checkpoint.

Also, forget about manning the browning guns. The first scripted sequence where you can use one, go prone and wait a couple minutes instead. The second time, just use your rifle.

And if the enemy is spotting you while you crawl past them, try crouching or even flat-out running. You might be surprised how often it is more important to get to cover quickly than to keep a low profile.

Edit: One last thing. The difficulty-related achievements DO stack, but once you get to the end, just don't press the guide button for any reason until they've all unlocked, one by one. Otherwise, you might interrupt the process. If you beat it on Hard in your first playthrough, they'll unlock in this order...Act IV Complete, Easy, Medium, then Hard.

This guide is solely to get you past the hardest point in the game on Hard difficulty. Zoku Gojira's guide works well for everything else you need to do on Hard difficulty, but he skims over the part where you first get to man the Browning gun. It is the mission where you must infiltrate the enemy camp and find a radio. Once you get to the radio, that is a checkpoint, and there is a health kit on the wall there. If you don't have full health and 5 health injectors, I'd seriously recommend starting the chapter over.

Next, you will exit the trailer, walk through a hole in the fence and then have to run up a hill while being shot from behind by nearly impossible to see enemies. RUN! and inject yourself if necessary.

Once you get to the top of the hill, this is another CHECKPOINT. If you don't have 95-100% health and 3 health injectors left, you should consider starting the chapter over. You can try beating it a few times, but if you can't, start the chapter over.

This is the hardest spot in the game. You have to defend yourself for 2:00 minutes and then exit down the back of the hill and run down the road there.

From the CHECKPOINT, you will be immediately shot at and spawn killed within 5 seconds every time if you don't do it right.

Here is the layout from the CHECKPOINT:

1). There are about a dozen enemies at long range BEHIND you. They are almost impossible to see, but can see you if you are standing or crouching and they are DEADLY accurate. Don't bother with these guys.

2). Then there are two or three guys across the road to your one o'clock position. If you spawn and run forward, these are the guys that will kill you immediately. These are the guys you must hide from. They may run up and try to find you, but on a good run, you shouldn't have to kill them.

3). Lastly, there is one guy to your nine o'clock position, but he can't see you when you spawn because he is on the other side of the crest of the hill. Easy to find and easy to kill.

With about 0:20 sec left, two trucks carrying troops will show up as well as a helicopter which I believe is no threat. Also, a few enemies will show up on the backside of the hill between you and the exit of the level, you will have to kill these guys.

So here is the script to survive 2:00 minutes from the CHECKPOINT:

1). Drop to the ground and go prone. Try to get into the shadows to your left and hold still while you wait for your alert bar to diminish COMPLETELY. You will be shot at, and this will take several tries to get just right. Use injectors if your health goes below 50.

2). Once your alert bar is totally gone, pull out your pistol and start crawling to your left and slightly back. Keep scanning the crest with your reticle until it turns red. This is the guy at the nine o'clock position. Kill him and continue crawling up around to the left.

3). The sandbag fortification with the Browning gun also has a health kit with more injectors, so you should crawl around the front and to the back-left corner to it and load up.

4.) Keep slowly crawling towards the back of the hill the whole time. Keep your pistol out and keep scanning to see if there are enemies near. If you get any blips on your alert bar, stop moving, backtrack, and keep to the grass and shadows.

5). Eventually, you will encounter the few remaining enemies that spawn at the back of the hill. Kill them quickly (I think I used the rifle + focus mode), then get up and run as fast as you can towards the road while injecting yourself as needed.

6). You will see a "distance to objective" display. Do not despair, the cutscene will begin WELL before you run that distance.

7). That's it! This will take a lot of tries, but be patient and try to learn where you can and can't go. If you have any questions or find any inaccuracies, please feel free to ask!