The Insane Difficulty is locked when first starting to play this game. In order to unlock this mode you must beat the game on once before or join a co-op game (the host only needs to have Insane unlocked).
You must beat every chapter inside of Act 5 (in Insane mode) to unlock this achievement. You are allowed to play the chapters in any mode: co-op, single player, or a mixture of both. The achievement will unlock as long as you have credit for beating each chapter in act 5 playing on Insane.
If you are having issues beating this mode by yourself I would HIGHLY recommend playing with a real person other than AI. It will make your progression through the game much easier.
Desperation (Act 5):
CHAPTER 1 - Special Delivery
Pretty straight forward and quick chapter. Take cover (there is PLENTY OF IT) and use longer range weapons (hammer burst or lancer) to take out enemies on ledges and on the ground. View the video below (first one) to see it in action.
CHAPTER 2 - Train Wreck
Part 1 - In this chapter they allow you to stay back and take cover. I would recommend you taking advantage of that. You have to watch out for the Theron Guards since they can do major damage if you get stuck. Once you attempt to open the door you’re going to have to fight a Berserker and in order to kill her you’re going to have to get her in the back of the train. Once in the back of the train blow up the tank to obtain total victory. Make sure you grab a bow to take down the Reavers.
Part 2 - Once inside for the first time you’re going to need to be VERY careful. Take cover on the right side and watch out for Reaver on the outside from both ends. Lancer and the bow take out Reavers very nicely.
Part 3 - Once you start to go outside again you’re going to have to try and stay back, so that means staying inside and shooting outside. This is not very hard and not many enemies.
Part 4 - Once you climb up to the top of the train and your outside you will be attacked by several waves of Reavers. You can use a lancer or bow against them. You also can work your way to the back of this near (towards the back of the train) and hop on the gunner. You’re still going to make sure you take cover and make sure you watch both sides.
Part 5 - This starts on the third video. Not too hard you’re going to be killing a bunch of Wretches and a few Reavers. This chapter ends just after you get locked into a room with multiple waves of Wretches dropping from the ceiling. Not a big issue here just use the shotty/melee to take them out. Also some people like to chainsaw them so have at it. Make sure you grab a bow for the last chapter (your second weapon can be either a longshot or lancer)!
End of chapter.
CHAPTER 3 - Pale Horse
This is it... big fight here! You will want to use the cover right in front of you (the light will protect you from the Kryll). Use your bow to get the Kryll away from RAMM and then switch to your longshot/lancer and blast him away. Once the Kryll come back switch back to the bow. If you can and get a good shot toss a 'nade into the mix.
Once he starts getting close launch a 'nade at him and then run to the other side. You're more than likely going to have to run to the other side if you're playing solo. If you're playing co-op is it easy to kill him before he gets to you (one using the longshot and the other using the bow).
Remember use the torque bow to get the Kryll away from Ramm and the other player needs to give him a healthy active reloaded headshot.
A final remark from olde fortran 77:
For what it's worth, it took two of us about 25 tries to get this, and we have no idea why we succeeded that time but not the others. Basically, we stayed behind the first bit of cover and torque bowed and snipered him until he got to the other side of the cover (like, one meter away). Then I blind tossed all 4 grenades and the other person torque bowed him and it was over. I swear there were times we put more rounds into him and still didn't make it. I think the grenades are very powerful against RAAM if you can get them on target.
Here are some tips if you’re having trouble:
- Become good at active reloading. This makes the Locus drop so much quicker.
- Take more cover. Not only do you heal but the Locus do not.
- Work as a team (if you’re playing with a person) and try to aid your AI partner (he will help some but there are issues with him getting killed allot).