The amount of hate for Linkin Park in this thread just baffles me. They brought Nu Metal to a whole different level. They weren't the best live performance when they first started but definitely improved over the years. I loved their first studio album.
I'm also seeing Pearl Jam and Queen which is even more baffling. I'd love to know what sort of music you actually listen to then. Freddy Mercury's voice is stunning and they changed the way songs were written.
Even Slipknot, while I can understand it is not your type of music, calling it the worst band ever is a tall order. Corey Taylor has an amazing voice and Joey Jordison was one of the best drummers in the metal scene.
I wouldn't know what I think the worst band is, but I agree fully with Curl-6's list of awful performances.
I try to avoid music I don't like so I don't really know what's out there that I hate. Things like Aqua or The Venga Boys or Take That come to mind. Never mind more local 'performers' like Eddy Wally or Zanger Rinus.
To give some perspective, some of my favourite bands or performers are Tool, Staind, Gojira, John Mayer, Hernán Cattáneo, Ludovico Einaudi, Victor Wooten, Rodrigo y Gabriela, Children of Bodom, Bobby McFerrin, Clutch, Metallica, John Butler Trio, The Dead South, Eminem (more so early years), Vektor,... this list is endless really :P