2.Go to the cheats, find and enter these words "WANT THIS DARK REALITY TAINT QUEEF" always make sure the last word of the cheat is still highlighted and press enter, a notification should appear saying cheats were unlocked.
3. Restore health, ammo, and rage if u want, but for this just go to unlimited rage and ammo. Also, get the unlock all powers and unlock all gun modes.
4.whenever u face a powerful boss or enemy, just stay within a safe distance*not too far though*, use your powers to freeze time*right 3 times*
5.press R2 until you find the Blood Hammer gun( this is the most powerful gun in the game) and lock on with L1.
6.shoot at them about 6 times, and press down to turn your powers off, this will unfreeze time and allow the shot to go to them and instantly be killed.
Really hope this helps, i finished the game in under 4 and a half hours using this( thats not alot considering how long the storyline is on the game)