Psycho Break

Play Chapter 7 under the Survival difficulty setting. While progressing, conserve as much ammunition and trap parts as possible. Take advantage of the existing spike traps to kill various enemies. If done correctly, you will encounter the Keeper boss with about 30 traps and a decent amount of ammunition for your various weapons. Start the Boss battle as usual by shutting down the poison gas. After closing the final valve, remain in the area and keep fighting. The Keeper boss will keep respawning from the safes about thirty times. Keep defeating him to get 2,000 Green Gel each time. With fully upgraded damage on your harpoon bolts and pistol, only one hit with each of those weapons will be enough to take him down. By the end of all the fights, you should have collected about 70,000 Green Gel. Note: You cannot damage Keeper for a few seconds after he spawns. To get more trap parts, use the Keeper's barbed wire mines. Simply wait for the Keeper to deploy his mines then kill him. Then, use the free time during his respawn to disarm the mines. Note: Keep a sniper rifle or shotgun in reserve in the event that you run out of harpoon bolts.

Complete the game once, then use as much time as desired to get the remaining green gels for all the upgrades. Also salvage parts and ammunition. When your ammo and skills are ready, start a speed run in New Game + mode from Chapter 1 under the casual difficulty setting. Starting a New Game+ from any other chapter will retain your previously recorded time, but starting from Chapter 1 will reset all subsequent times. Once started, play as fast as possible. Keep in mind that cinematics will add to your time; skip them whenever possible. Skip collecting gel, and get ammunition only when it is in plain sight. Go to the safe room only required. Save the rocket launcher and Magnum for Bosses, along with incapacitating bolts.

Collect all map fragments and successfully complete the game. Start a New Game + mode game with the cleared game data. After you can enter the back area, go to the right where the map fragment holder is found. It should be glowing red if all fragments were collected. Interact with this map and an attaché case will appear on the nearby table. It contains the High-Powered sniper rifle.

Successfully complete the game under any difficulty setting. When you play that same difficulty again, you will retain your previously obtained weapons, items and upgrades. The enemies in New Game Plus mode will have an increased difficulty.

Successfully complete the game.