I hesitate to say "worst band". As has been said, even good bands can have bad days. So I'll say worst performances. I've been going to concerts for over 45 years and I've heard a lot of good and some bad too. I've only walked out of two shows before they were done. Robin Trower back around '75 or '76. He was so stoned I could see the red glow from under his eyelids from 100 feet away. Very lackluster performance. His opener (Starcastle) on the other hand, was GREAT! The other concert I walked on was Jethro Tull in I think 1998. I'm a big fan of Tull but just could not get past the horrible mix coming out of the PA. I couldn't tell you if the performance was bad or not because I couldn't hear it. The opener at this show (ELP) sounded and performed GREAT! It was an outdoor show with separate stages/sound systems so I'd say this was mostly on their engineer. I was also not impressed by their decision to stop in the middle, drag out ratty furniture, and do acoustic versions of the guitarists solo album.