I can’t

All of my characters are at level 99. I have one job at 99 and the rest of them at 25. I have +5 and +6 weapons for my party, dragon armor for all of my characters, and have as many healing items as possible. But yet, I still cannot beat Amon in the true final millennium tower. Once he summons the thought entities and uses the orbital laser, my characters easily get knocked out before I can barely beat Majima, even while using their weaknesses. I also have courage pendants and talisman equipped as well. Any advice to beat this so I can finally move on from this frustrating battle?