I don't know how anyone can "hate" a player for "no good reason." That being said...
Any player in pinstripes (Bernie Williams was the one exception). Any player in a Red Sox uniform. Any player in an Oakland A's uniform. Any player in a Dodgers uniform (Mike Piazza and Clayton Kershaw are exceptions).
Brett Boone, Rougned Odor, Wade Boggs, A-Rod (because he killed the Angels), Lenny Dykstra, John Rocker, AJ Pierzynski (of course), Ian Kinsler, and I'm sure there are others...