Music artists that were once terrible, but became great?

The flipside of another topic, which artists started out bad or meh and then became brilliant?

Best example of this for me is Carly Rae Jepsen.  Not a single thing worth a damn on her first two albums besides one novelty hit, and then bam, she released Emotion, one of the best pop albums of all time, and then she followed that up with Dedicated last year, another of the best pop albums of all time. 

Midge Ure was in a boy band called Slik. Went on to great things with Ultravox.