My worst concert-going experience was actually for a band that I was in.
We were, at the time, one of the innumerable struggling Boston bands (I lived in Allston, where you can’t trip and fall without hitting a guitar player). The venue was a starter venue, to be sure; however, we had begun to make a name for ourselves, and confidence was high that there would be a cornucopia of attendees.
The fans did not disappoint. By the time we arrived, there was a good crowd already there. The band was pumped - we prepared to give an earth-shattering, high energy set. Then, as we spoke to the bar manager to get the ok to begin setting up, the horrible truth was revealed.
They had double-booked that night. A DJ was about to set up, and we would not be receiving any stage time whatsoever.
We managed to restrain ourselves from throttling the manager, and immediately began damage control… but there’s only so much you can do. Sure, the audience knew full well it wasn’t our fault, but they had spent their time and energy to make it here, to this show. Some of them, I’m sure, never ventured out to see us again. To add insult to injury, the band ended up having to stay for the whole lackluster DJ performance (not a dig against DJs in general, just this specific one) in order to spot our fans coming in, so we could explain what happened.
Several months later, I did a solo gig at the same establishment, under “new management”, and was paid with nothing but two tickets for a free drink (I realize that doesn’t exactly fit with the “worst concert” thread theme, but since I’m already complaining about the bar, I figured I’d go ahead and toss it in).