Quote Originally Posted by _yeojina_
Str: Flare
Def: Protect
Spd: Haste
Luck: ((Nothing here, I didn't know what it was!))
St Atk: Pain
El Atk: Demi
St Def: Ultima
El Def: Quake
My brother had something junctioned to Rinoa so that when Griever did Shockwave Pulsar, she took no more than 500 damage.

Luck, like Endless says, effects critical damage and hit% rate. I think it also effects types of dropped and stolen items, like bahamut's rare item abl. does.

Death or Triple work well junctioned to luck since you use neither spell in your demo.