As soon as the fight begins, notice the VS will fly around while doing various little spinning attacks. Fly towards him while holding L2, then release when next to the Boss (to do a horizontal slash). You'll take a significant amount of health from the Boss. Sometimes you can also score a second hit this way, but be cautious of the homing missiles. The Boss will dart around shooting little lasers at you, which are easily avoidable by simply following in his direction to miss the attack. When the boss reaches around 30% health it will call up two laser weapons that do massive damage if they hit you. One is horizontal and the other is vertical. Notice when he gets ready for this attack that he will throw his arms forward. Use it as your cue to get as far back as possible. The range on the lasers are fairly small. When he is done, he will stand still for a brief moment and shoot missiles from his shoulders. Take this opportunity to go in and deal some damage. The Boss does not have much of a pattern. Remember to hold L2 until you are directly on him and release. Around nine well-placed slashes are required to defeat the Boss.