make sure you have elixers, second chance, once more, Ultima Weapon, and Trinity limit, also beserk charge helps, but only if you know how it works, and make sure you have all of teh growth techniques.
start out blocking his attack with the reaction command then use trinity limit.then just wait for him to use the attack again, then just beat him up till you get ur MP back, when it get restored use trinity limit again, believe me this helps ALOT, relfect helps when he is using the spheres, but you can always use arial dodge to get away from them. when he tries to use sin harvest, just glide over to him and attck him, if you dont make it get an elixer ready so that as soon as the attack is over, you use it. just repeat till he's dead.