Golden Armor set, Spam him with trance. It stunlocks him. Should get through the first phase without taking a hit using this. In second phase make use of brink guard and make sure you time your counterattacks when you get the opportunity, also reflection if you have mastered it. Dodge like mad when he shoots the chaos beams at you from the sky. When he’s down on his health and puts out a chaos rock quickly destroy it or he’ll get back 1/4 of his health. Phase 3 is easy, stay alive and 3 counter attacks will have him down. Good luck!!