Anyone who clearly doesn't put in the work to the best of his ability to improve his flaws or who has a selfish approach to the game. A guy like Alfonso Soriano strikes me as such a player. Also don't care for Carpenter (whiner) or Hughes (psychopath) and Molina (showboats at times) gets under my skin but the latter IMO would be a guy we would all back if he were a Red from the beginning so why get all worked up because he stood up for his teammates? Carpenter I just don't like because he is a legit crybaby.
But trying to think outside the box I'd go with Cam Newton (everything that is wrong with sports), because I just cannot think of anyone worse than Chris Carpenter in Baseball.