#5 Edge
Edge, for a long time in his career, was never given the main event push. But when he won the Money in the Bank his career took off. Ever the opportunist, Edge was able to rack up great wins against some of the greatest of all time and become a multiple time world champion.
What worked for Edge? Turning him into a heel. Pretty much throughout his first stint Edge was (for the bulk of it) portrayed as a face but as soon as he got pushed for the main event the character got darker and darker and he just revelled in the heat he was able to generate.
He was the eternal Bad Guy for the company and even though for a brief time he was turned face when he returned to win the Royal Rumble, WWE quickly realized their mistake and turned him again after the ovation he received was at best Lukewarm as a Face.
In Edge's case, one can say his career completely changed once he turned heel as he cemented himself as one of the modern-day greats of Wrestling by winning the World Title 11 times.