Pink because she was always the underdog
Kelly Clarkson because she was a talent show winner
Britney and Christina because when they debuted people thought they were just part of the bubblegum teen fad
Well considering that Shakira, Beyoncé & Brit are the ones who debuted in the 90's and they're still getting hits, decent sales, etc. They're my answer.
Shakira well at least in America, seeing as only Gloria Estefan did it before her with being extremely successful in both english and spanish speaking worlds.
Kelly Clarkson because not a lot of reality tv show contestant winners go on to have huge consistent success.
&
finally Bey, yeah she was the lead singer and got the most spotlight. But even with that said plenty of members in groups that try to go solo fail.