Penn is a legendary figure in MMA, as revered for what he accomplished in MMA as for what what he didn't. Penn is one of only two, two division champions in UFC history and his capture of the welterweight title from then pound-for-pound kingpin Matt Hughes is one of the most iconic moments in the promotion's history. His mercurial nature led him to vacate the welterweight belt in search of bigger game, and though he did eventually return to the UFC and claim the lightweight title in his career defining run, Penn's forays outside of the lightweight division means he is still one of MMA's foremost cited cases of "what could have been.