Carlos Zambrano and Derrek Lee
Carlos Zambrano definitely had (and we'll say probably still has) some anger issues. During a 2010 inter-league game against the White Sox, the Cubs pitcher went bananas on his first baseman, Derrek Lee. Zambrano went all UFC in the dugout after an inning in which he gave up four runs; Zambrano was apparently mad that Lee hadn't gone all out on a grounder. And this is when the Cubs were sort of good (for the Cubs).
You have to give Zambrano credit for taking on the 6'5" Lee—maybe there was real beef there. After the incident, who was Zambrano's biggest defender? Naturally, that was then White Sox manager and fellow tempermental nutjob Ozzie Guillen.