Neither. Luck only matter in the short run, and in order to be "the biggest loser", someone need to play a lot. As for skill the worst players are generally found at the lowest stakes like 1/2 live cash games or online microstakes games. But these players can never be the biggest losers either, because they play for insignificant money. The biggest losers are people like Gus Hansen and Gui Laliberte, who were neither unlucky or bad at poker, but they played for a lot of money against someone, who were even better than themselfes.