F.E.A.R. Files

Youtube user QBS216 recorded 80% of the campaign on extreme, and it's very handy.

http://www.youtube.com/profile?user=QBS216&view=videos

The last few levels aren't horribly difficult. You should finish every enemy encounter with at least 8 medkits. If not, suicide and try again. Take your time and abuse slo-mo.

For the epilogue, try to use as many auto-turrets as you can. Keep on the move and use cover. There are tons of medkits, grenades and armor to pick up. There will only be one mini-gunner, and one heavy armor.

Achievement unlocks at the credits.

This is BY far the easiest campaign out of all FEAR-games.

Aside from a few encounters where it's slightly dark and the Minigun-Juggernauts you shouldn't run into any issues whatsoever.

For the later the game usually provides more than enough ressources beforehand so they're not halfbad either. The first can be semi-cheesed by setting up a couple of Claymores and Remote bombs behind the corner and then aggroing him resulting in an instant death when the charges go off.
The other ones are slightly trickier, but it all boils down to yeeting your nades or putting a turret opposite of you to make him turn your back on you.

For weaponry stick to the G2, Shotty and whatever you feel comfortable with until you get the Minigun. After that, you can use the Rocket-launcher for the Mechs or shoot em with the Minigun to save same backtracking/time. Your choice.