Vijay Singh. I followed him and Jesper Parnevik for about 6 holes of a practice round at Whistling Straits for the 2004 PGA and he was a royal ass to everyone, refusing to sign autographs, even to kids, and becoming very obviously annoyed with Parnevik for being a decent enough person to sign for everyone who asked him for one.
Phancy Phil Mickelson. I just hate almost everything about him - his slighly effeminate voice, way of talking and mannerisms, his nonchalance about routinely gambling more than the average family earns in half a decade, his arrogance, his awkward attempts to be pleasant and personable, his choice of dress pants for athletic attire, etc.... I have absolutely no idea how so many average joe golf fans like this guy who very, very likely views average sorts of people rather contemptuously - attempting and often making risky going-for-broke shots shouldn't count for that much popularity.