He was a freaking Sith Lord!
So? In an order of two being a Sith Lord isn't really anything special. It's just a title. It's like people saying Lotr > Starwars because gandalf is a god or some sh*t liek that. Titles don't mean anything. Besides, Mundi was a "freaking" Council Member. A much harder feat to attain.
And two can use the "absence of proof isn't proof of absence (Which it is proof, actually.)
I think C-3PO > Maul. Just because we haven't seen any showings of C-3PO's pwnge doesn't mean he doesn't.