Use the water in the middle. The Boss for some reason cannot go into the water. If you are in there, you can get to the correct location and hit him from behind. Finish the stage before this with a Record Control. Fill up your Sweeper (do not use any on him yet). Then, go outside the gates. When he shows up, pick up what you need to get a Pause Control. Make sure you are close to and in front of him, then use your Record Control. Run past him and keep running. When the Record's power up is done, the recording will play. While the boss is chasing it, hit him from behind and repeat as he becomes normal. Next, use Pause in front of him. Run behind and shoot him. This works even better if you start off with multiple Pauses or Records.