Cerberus

Before, Cerberus was the only boss in the game that I had to turn down the difficulty for. So, how are there any tips on how I should beat him (party composition, Personas, items, etc.)?

Another weird thing again.

First off, I should mention im still on my file with my Game Genie Cheated LV99 character. I got to the bridge where you encounter Pascal Cerberus. I have the Golden Apple in my inventory. He returns to his senses, but then he just says pretty much "thanks, see you!" and leaves. I only have 8 demons in my comp. I even reloaded the save and took one demon out of my active party and still no luck. Am I missing something? Or am I too strong to have my loyal buddy back?