I admire your tenacity.

Little internet browsing:
YouTube - Xenosaga III - Chapter 9.8 - Battle with Margulis (Part 1) (skip to roughly 3:20)
YouTube - Xenosaga III - Chapter 9.9 - Battle with Margulis (Part 2)

Also, gamefaqs
GameFAQs: Xenosaga Episode III: Also Sprach Zarathustra (PS2) Boss FAQ by coutach
GameFAQs: Xenosaga Episode III: Also Sprach Zarathustra (PS2) FAQ/Walkthrough by beefybuffalo
GameFAQs: Xenosaga Episode III: Also Sprach Zarathustra (PS2) FAQ/Walkthrough by Tomas

Among others, and do a page search for E.S. Levi.