I dunknow if I can pick just one
As much as I love Motley Crue, Vince Neil is a poor singer and the weakest part of the band. Live, he forgets and misses lyric and his studio vocal has little range. But the band as a whole covers up for his downfalls.... ****, we all know he was only in the band cuz he was Tommy's high school buddy.
I think, again... as much as I like GN'R, Axl has a pretty annoying sound. His vocal works best on his own tunes, but it really makes me cringe when he performs cover songs. Way too much weird stuff going on with his style... it's a shame that the chorus to Knockin' On Heaven's Door has been permanently scarred.