From the artists I mostly listen to, the ones that come to mind are: Shola Ama - went from million selling debut to barely scraping Silver with her second album (which, by the way is an amazing album). Dido - two huge albums and then that third album... Nelly Furtado - I suppose she also took too long of a break between albums. Duffy - mentioned several times in this thread already but I'm still shocked at just how bad her 2nd era performed. Plan B - I know Ill Manors is technically a soundtrack album and not meant to be as commercial as The Defamation, but he really did seem to go from one extreme to the other in terms of sales. Eternal - went from a multiplatinum Greatest Hits to missing the Top 75 altogether just two years later. And my faves En Vogue - going from a Platinum era with EV3 to the abysmal under-performance of Masterpiece Theatre (albeit yet another excellent album). Although one could argue that they would have flopped a lot sooner if it wasn't for "Don't Let Go (Love)" giving them a temporary reboot.