I've seen a few that suck live, but one that bothered me was Aerosmith. Late 80's or so. One of the worst live shows ever. Not because of the music but Steven Tyler's vocals on stage can NEVER match what he does in the studio. The reason for this is that the studio vocals are HEAVILY editted, cut and pasted, spliced, diced and over produced.
Don't get me wrong, I love me some Aerosmith, but on that day I realized that I'd probably never spend another dollar on Aerosmith tickets. That was about 20 years ago, so I'd probably go back on that thought and perhaps see them again if they toured, but my expectations would be fairly low, at least for Tyler's vocals, definitely not for his stage presence