At the old club I saw Helmet and Jawbox...that was insanely loud. Believe it or not, Oasis' volume at the old club show was pretty insane too. They had so many amps on stage that you couldn't see Tony McCarroll behind the drum kit. If you were near the stage, you were blasted away.
At the new club, I'd say the loudest shows have been the Prodigy (even in 1998 the volume and bass was just insane), Ministry in '04 (my ears were slightly ringing the next day even WITH ear plugs in).
I've seen loads of other shows that were beyond loud (Sugar, Dinosaur Jr., Beastie Boys w/L7 come to mind), just not at the club.