Dark Sector

This achievement is earned through normal campaign game-play. Please watch the videos for an idea of how the level is laid out.

This is the longest level in the game, and a real pain on Brutal difficulty. Spend a few minutes to familiarize yourself with the videos, and move slowly ahead and eventually you will reach the end of this very long level, with one hell of a cool boss battle at the end. Keep an eye out for the splashes as it starts running towards you :D Make sure you are well-versed with the power throw as you need it to stun the thing. Eventually you will will make him stop running at you and he will start climbing the pylons in the room. He attacks here are very deadly, so make sure you pay close attention when he starts coming at you.

After you defeat him, you will gain the invisible perk, and that makes the game a touch easier... until you start chapter 8.

The Korbov TK6 will be available this chapter, but at the pricey cost of 40,000 rubles (this is why you saved that money). Its far more effective than the AKS-74, outranking it in both damage and accuracy. Load it up with upgrades and enjoy the firepower. At the end of the chapter you'll face the Stalker. Watch the water for signs of it moving and just keep hitting it with your gun and glaive. When it retreats to the corner be sure to shoot it so it runs right back at you, keeping it from coming around behind and getting a surprise attack. It will run up one of the large spires, and at this point you'll want to keep looking around in a circle, as it will materialize and fire rockets at you pretty quickly, and these can be devastating on brutal mode. Use your shield ability to deflect the rockets back and finish it off when prompted.

(The video belongs to BonersGames)
(FYI i used http://www.xbox360achievements.org/game/dark-sector/guide/
credit belongs to wickeddark)
(before you give me a "thumbs down" on this or any other solution. Tell what I can do to fix it)