hard to say, people have good days and bad days and I cant make the distinction for anyone based upon a bad performance,,
most entertainers I have heard have good performances and bad ones,, so,, I can just say whose STYLE of singing isn't my cup of tea
bob dylan
james brown
and
william hung,,,lol
shoot-me-in-the-head-please,-Bob-Dylan, bah..
He must have been chronically depressed.
As for bad singing, I love Within Temptation but the live stuff I heard was friggin awful! Sounded like someone was strangling a cat