I can’t think of a bad performance but the worst concert experience was seeing Peter Paul and Mary at the Greek Theater in Hollywood. PPM were great but this jerk sitting just in front of my friend and I took offence that a couple of Marines would come see them. Ran his mouth for a while before his girlfriend got him to shut up. On the way out he made a point to catch up to us and start mouthing off again. We ignored him until he grabbed my shoulder to spin me around. Somehow he broke his arm and probably some ribs.
Hell of a downer after such nice peaceful music.