In the docks, where you have to battle the 'Insane' Torque, find the .50 cal machine and shoot him with it.
On the last level, you are isolated out on the docks and have to fight the monster that is your alter-ego. Make sure you have your shotgun (in the trailer in the preceding level). Immediately as he appears, shoot him. Walk forward, to the right, and up the ramp going to the fenced off piece of land. Run towards the fence and to the left. Walk off the land where the fence ends. There is a little shelf of land that you can stand on. On all difficulties except 'Impossible', you can stand on this shelf and shoot the monster until he dies. It takes about sixteen shots from the shotgun. You can then jump back on the land (this may require several attempts) and deal with the hypo-monsters. The best way to kill these is to shoot the ammunition boxes that are spread around the level. You can also throw bombs in their vicinity to kill them. If you are playing under the 'Impossible' difficulty setting, you can drop down to the shelf of land but must move up a couple of yards or the monster will jump and you will be thrown into the water. Once you are safe, he appears for a few seconds then runs down to the main dock then jumps repeatedly. Eventually, he comes back. You can shoot him with the shotgun and throw cocktails at him until he dies. The big monster at the end is relatively easy to kill. When coming from the fenced-off land back to the dock, there is a fenced door to the right that you can kick open. In three of the four places where the monster appears, you can hide out and not be hurt. If you are energized with the blue plasma, you can throw the plasma at him and avoid being drawn close. When he attempts to shoot fire at you, jump back to avoid being burned. There are boxes to hide behind if he comes up on the side nearest to the fenced-off land. If one of his whirling blue spirals hits you, just shoot at him in slow motion as he tries to hit you until you are a safe distance way. If you are a good person throughout the game, a man arrives in a boat and you will jump aboard to get off the island. If you are a bad person (i.e., shooting potential allies and everyone else that you encounter), the ending changes. You will throw a big box at the man who comes to rescue you (sinking his boat), change into your alter-ego, then go back towards the prison to apparently fight everybody who attacked you on the way. The alternate beginning involves you being put into a prison cage and changing into your alter ego (monster) after you have been provoked.