Final Fantasy XII Zodiac Age - Exodus Esper

For the first part of the fight, go all out with weapons as long as you can. At about 50% HP he will cast Unleash on himself and his main attack becomes Scathe (may hurt you a lot). Cast shell on your party and be ready for a lot of healing/reviving.

The last part is when he is in critical HP and becomes immune to physical dmg and has Reflect. If you can dispel it then use magic on him. The physical dmg imunity will pass eventualy so you can finish him with weapons again. He also casts STOP which is not cool at all since you can't use Items. Stop will reset when that character dies. My advice is if you struggle in this part, set the gambits for survivability and just wait it out until you can do Physical dmg again.

If you attempt this with lategame gear, it won't be hard at all.