Damnation

Enter "Revenant" as a code to unlock the Insane difficulty. that way you only have to play the game once achievements are stackable also Enter "BlowOffSomeSteam" as a code to unlock a gun with a blade attached to the bottom of the barrel that kills in one hit. codes do not affect achievements

While the other solution is excellent if you don't have a co-op partner, Insane difficulty is made a complete breeze if you can play in co-op. Unfortunately, you cannot use the supergun in online co-op, but entering "Revenant" in the code screen will still unlock Insane difficulty off the bat, just as it would for single player.

That said, the biggest tip for co-op is to always have one player be the scout and rush groups of enemies and the other be the sniper and kill enemies from a distance. This is useful for two major reasons.

1) The scout can intentionally engage enemies and get downed with that cluster of enemies around him to make the sniper's job easier. Enemies do not disengage and/or look for new targets just because someone goes down. This makes enemies easier to snipe, or if you're lazy, to drop a trip mine on top of.

2) If the scout goes down, the sniper can use spirit vision to resurrect him from any distance. And because the sniper is sitting at a suitably far distance, he doesn't need to worry about being attacked while doing so. The caveat to this is that unless most of the enemies in a section are dead, there's little point in resurrecting because the scout will likely just get downed again almost instantly.

If you don't have a co-op partner, but you do have two controllers, the sniper can become your safety net. Just use him to resurrect yourself anytime you're downed, and you should have little problems progressing. The sniper will also be automatically teleported along occasionally when the scout advances, so little work needs to be done to continually reposition your safety net.

Update: Playing in split-screen co-op also has the added bonus of still allowing the primary profile to use the supergun while also having the safety net of a second player. Enter the code "BlowOffSomeSteam" at the code screen and you then have access to a one shot, one kill weapon.

In addition to the other guides here is what I found helped me.

While playing solo use cover and spirit vision. Don't discount the normal pistol - it will kill the enemies from a distance with relative ease.

The final boss fight was a pain in the ass for me. Before you get to the boss fill up on explosive arrows. When you start the fight run straight across the map behind the three buildings (through the third) then cut to the back of the map toward the tall building. Go behind that building to attack the boss. Use the arrows - fire then head for cover behind the wall. After you have done enough damage elevators will raise and enemies will appear. Stay behind the building until the boss faces away from you and concentrates on Jack. Make your way back around the building on the side facing away from the boss. Be careful killing the enemies - try not to shoot in the direction of the boss. I found that a couple of time he would face Jack and not turn toward me when I tried to do the jumping on the platform. If he does turn toward you stand behind one of the metal supports for the platform until you heal - he will loose sight of you behind the support. When you make it above him stand at the back and jump over the rail to catch the pipe - continue the swing and jump off to the crate. If you stop and have to get the momentum back he will kill you. I'm not sure how the second half of the boss fight is on single player because I finally gave up. He kept killing me on top of the platform. I restarted that mission on two player split screen. I kept Jack in the elevator in the back corner so he would not shoot her then made my way around as I had before. The enemies ignored Jack in the elevator and came after me - I used spirit revive to bring myself back. After the people were killed the boss would not even look at Jack - he kept his focus on me. I was able to walk by him using the second controller - he never even shot at me - I continued the process to drop the crate on him. After the robot suit was destroyed I ran the second controller up into the building to stay safe. Prescott never even took a shot at me while I was on the ground. I picked up one of the rocket launchers and killed him with ease.

My suggestion if you are having trouble on Insane - put it on split screen and breeze through.

Before attempting this your gonna want to go into the unlockables menu and enter the following codes: LockNLoad allows you to pick what weapons you start off with. BlowOffSomeSteam unlocks a gun that kills everything in 1 hit except the final boss & turret guys. you may also want to put in Revenant if you haven't unlocked insane yet.


ok now for the way to get through this: your gonna want to put on that one hit kill gun & a dark seraph rifle. pretty much just take your time and don't rush things, if you can try to let the computer handle most of the fighting while you hang back, snipe with either a dark seraph rifle & revive them when they go down. always remember to check things with spirit vision first before rushing forward and try to snipe enemies with the dark seraph rifle or the one hit kill gun.
try to avoid open conflict if possible because most of the time you will die before killing the guy or guys attacking you. this guide was made for those who don't have the benefit of a second profile.
the only real trouble I had was the final boss but I noticed sometimes he spazes out and doesn't attack even while climbing to go shoot the thingy holding up the container. I also noticed that the tank on his back that you have to shoot took way less shots to trigger the next half of the fight than it did on normal. I'm not sure if it's because I hit him with the one shot kill gun first or if it's just another glitch in the game.