one band i would like to say are TLC, started off as an ok pop band, but they were really developing with that album they did (waterfalls, red light etc) just before they went bankrupt and shit
the comeback stuff was alreet, but you can tell they weren't as good as they could have been if they hadn't fucked up the 3rd album so much
spose wu tang as well, they did really well, but they got so distracted with their own labels etc, still makes me wonder what could have been if they spend so much time helping out their cousins and mates, and mates cousins etc