First, get back to Elicoor II (or III, I forget)... Then Make weapons with Oricalcum smithed into them (get oricalcums by alchemy, oricalcum=500+ ATK), you should have at least 3000 ATK, then you might a have a chance,(ripe/perfect/magic) berries really help, The party doesn't really matter, just pick whoever's at the highest level, the perfect symetry is easy to outrun if you have bunny shoes, and that's pretty much how i did it...