I thought Rolling Shield was the only thing that even hurts Third Form Sigma. Call me crazy, but I'm pretty sure that's how it was in the original Mega Man X. I believe they changed it in Maverick Hunter so the X-Buster also harmed him, but I distinctly remember only Rolling Shield harming Sigma's Third Form in the original game.
Regardless, congrats on completing your challenge. I haven't done anything like this in any of my games simply because it sounds like way more effort to me then it's worth. Don't misunderstand, if other gamers like doing this kind of thing, that's cool with me. Just not my cup of tea.
_________________ The Local Video Gaming Lunatic
Recent stuff I'm into:
Watching: A Certain Scientific Railgun (ep.14, stalled), Hoshi no Kirby (ep. 71, stalled), Nazo No Kanojo X (ep. 8), Acchi Kocchi (ep. 8)
Reading: nothing