Nadal se la volvió a pelar a Federer en el Abierto de los Estados Unidos => Federer showed Nadal who's the boss once more in the U.S. Open
Me la pelé con las vacaciones de diciembre => I won't have a Christmas break, I'm such a loser
A popular way to express to someone that you think you're better is telling him or her "tú, a mí, me la pelas". If at the same time you move up and down your right or left hand (both only if you already master the one hand version) as if you were about to roll the dice in a board game, the effect is exponenciated. Any Mexican will get your point right away and probably won't let you walk away without proving it. Beware.