Double Flare Star is a combination of Trance Kuja casting Flare Star on his turn and using it as a counter attack, and this only happens when his HP is low.
Son of a bitch. Necroing this.
I just had my first try with Trance Kuja, Zidane, Dagger, Eiko and Amarant (what can I say, I like Summons as source of damage). Levels were 67, 66, 66, 64. Things were going very smooth, to be honest. He had casted FS once but it's manageable with Aura and other shenanigans. I didn't know (or rather remember) Ultima Weapon and Angel Flute absorbed Holy. I'd suggest clarifying that in the in-game dialogue (I can't really remember each detail of the Unleashed main thread).
And then he casts FS (I assume it was a counter, as Landon said). I survive with Zidane, Amarant and Zidane were the only ones with Auto-Life (bad turn management and lack of Auto-Haste, my bad). And then he casts another <.<. Zidane was at less than 100 health. He reraises, and then Kuja casts Flare, GG.
I don't know what I'll do with Curaga counters though <.< I like Dispeling his Reflect so he wastes turns recasting it, but I don't know what to do if all I do is Scoop Art, Aura, someone dies, and maybe the fourth one deals 4.4ishK damage. And then a Curaga coutner for 7K <.<
Now, I know normal Kuja in D3 will Spam FS to no end if you equip Auto-Reflect. Can I equip Auto-Reflect on at least Zidane here? I'll try that today.
I'm now I'm in a somewhat stalemate with Neutron (first try). In the current version, he uses Wall2 instead of Shell and Protect separately. Wall2 gives Protect + Shell + Regen, so it negates the damage you did when you're at a tough spot.
While you begin to build back up (while he uses Blue Shockwave, kills one character, evadable, or a tier 3 elemental magic party-wide), he regens his health back up (since the SOAB is killing off Eiko and I can't dispel Wall2), and then he proceeds with his signature move: Grand Cross and Neutron Ring. This happened 5 times already.
I've been saved once by Rebirth Flame. What in the fuck am I gonna do.
Mad props Landon. The battle as is is dynamic, and makes my bash my head against the wall.