You don't need to level up, I defeated this boss with the lowest possible stats, and even still it was a piece of cake. Just make sure you can get a few thunder spells in there once you regain your magic and summons. And if you ever need to summon an aeon to finish him off, use Ixion with an overdrive gauge already full, if possible, have Yuna's overdrive gauge full as well so that you can get a double overdrive in there. Easy.