Washington, DC -- As the WWE's reigning world champ, John Cena has seen many a villain come and go from the ring. But Cena tells AP Radio that he's never heard anyone get booed as much as Kevin Federline when the two went at it during a match a couple of years ago. Cena says the hatred that fans had for Federline would make him a good wrestler if he ever wanted a career. Cena beat the pants off of Federline, though Federline defeated Cena in their first match with the help of some other wrestlers. Cena currently stars in the movie "12 Rounds."