The 9 Yum Jen Ging and the 9 Yeung Jen Ging were the two top martial arts skills in the CONDOR HEROES TRILOGY. Golden Haired Lion King Tse Tsun posited that if anyone could master both skills, that person would become invincible. Cheung Mo Gei observed that perhaps no one could pull it off (except maybe Cheung 3 Fung, but Cheung Mo Gei wasn't certain about that at all). In any case, no one ever did master *both* skills.
But just how powerful do you believe a person who did master both skills would be? Would that person truly be invincible?