Hard to say which was really the worst, but here are some contenders:
Meatloaf.Sheffield Arena early 90s.
Wife told a mate I liked him, they got a ticket for me between them. I was too polite to turn it down. He's shoot.
Simply Red. Sheffield Arena. Early 90s
Wasn't until I got there that I realised I really really loath the red haired little cabbage toothed tosser, and his music is dreadful, truly dreadful.
Icicle Works, Sheffield Poly. 1984.
They're shoot.
Gary Glitter, Sheffield Poly, in the days before hard drives and computer repair shops.
Came on stage, looked wide-eyed fat and sweaty for ten minutes while the band did their thing, then f*cked off and didn't come back. Tnuc.