FINAL FANTASY XII THE ZODIAC AGE

Easy way to kill this guy is to have a gambit set to always cast reflect on all characters. You have to change the gambits to use healing items instead of magic.Have a gambit set to cast Slow and Bio on him as well as he is vulnerable to that.I used Fran and Balthier as they were my ranged characters (bow and gun) and used Ashe as my magic caster.Hide the character you control (Ashe) behind the rock in the middle of the area, and let the other two just attack.Fafnir is weak to lightning, but his fave attack is Shock, so reflecting that back at him was doing around 10,000 HP damage every round.He basically killed himself!

Use ranged characters as if someone is close he will use White Breath instead of Shock. Takes a while as he has around 1.3 million HP, but very easy.Make a drink, read a book, and so on.

I tried many methods of hiding behind the rocks and stuff, and kept struggling for some reason. This method linked on YT though worked FLAWLESSLY the first time for me. I take no credit for it.