For example: Led Zeppelin is a good band, even if overrated. But many songs of them are almost ruined by the terrible voice of Plant. His screaming and moaning during many of their songs is ridiculous. Take 'Whole Lotta Love' for example: what the hell is supposed to be that fucking moaning? I find it embarrassing to listen to that song with someone in the same room.
Led Zeppelin is a good example of a band sabotaged by a poor vocalist. Plant = the weakest link. I like the instrumental part of Led Zeppelin's songs.
Many people hate U2 esp. because of Bono. But excuse me, Bono has a voice 100x better than Plant.
Any other examples?