L
the worst i've seen was macy gray opening for santana in 2000. you can picture the aging tye dyed crowd all simultaneously scratching their heads in confusion.
Worst I've seen was some metal-sounding band opening up for Rusted Root around '03-'04, I think. Never got the name of the band because frankly I didn't give a shit - they were fucking horrible and a bad mix for the event. I sat in a corner with my wife with my head down on a table covering my ears and trying to take a nap until RR came on. Pretty pathetic.