Persona 3 Portable: Margaret Battle

Margaret is a boss from "Persona 4," and they added her to "Persona 3 Portable" for an extra challenge, as if Elizabeth/Theodore wasn't tough enough. Her battle is also a puzzle, but with several phases.
To tackle this challenge, you will need:
All characters level 99
"Great" Status for increased chance of critical hits
Orpheus Telos with high stats and the following skills:
Thunder Reign, Mind Charge, Salvation, Elec Boost, Elec Amp, Unshakeable Will, High Counter and Sharp Student
One Armageddon Item (can be traded for at the antique shop or won from the Hanged Man Vision Quest)
Strong weapons and armor. Accessories should block the characters' elemental weaknesses, and the MC needs the Divine Pillar accessory (Heart item earned from Alilat). Do NOT equip the Omnipotent Orb, or she will OHKO you.
Marge has 4 phases. If you don't do enough damage (about 7,000 HP) within a set amount of rounds, she will OHKO you. She also gets 2 attacks per round.
Phase 1: Physical attacks. She is immune to whichever type of attack she uses on her second turn, so attack with the other 2 types. If your character can't do that attack, us a buff or heal instead (I brought Aigis because she can buff all 3 stats).
Phase 2: Bad status. She can be hurt with any kinds of attacks now, but pay attention to what she inflicts on you. Cure Charm immediately. Cast Thunder Reign to shock her and let the rest of the party attack for easy criticals.
Phase 3: Elemental Magic. Marge will be immune to every kind of attack except for the opposite of what she casts on her 2nd turn:
She uses lightning, you use wind, and vice versa.
She uses fire, you use ice, and vice versa.
If you characters don't have those elements, use any elemental gem items you've picked up to keep the damage going. If she uses wind, Orpheus Telos's Thunder Reign will give a nice burst of damage.
Phase 4: Endgame
When Marge casts Power Charge and Mind Charge, you can go hog wild; just be mindful when she casts reflect spells on herself. You can also just use an Armageddon item to deal 9999 damage and end the fight quickly.
Thanks to KADFC for the strategies.