Without a doubt, Van Halen 1992. I was, at that time, really into Sammy Hagar, especially his VH stuff. Man, they just sucked!! Sammy was terrible, the song selection was horrible. They played way too much stuff off of the then-new F.U.C.K. album.
Although most of the crowd didn't appreciate them, the unknown opening act blew them off of the stage. Why would the fans appreciate Alice In Chains???