Professional wrestling seems like a particularly easy industry for grudges to develop in. This is a world based around pretending to fight, after all, and all it takes is one particularly snug shot to land for a lifetime of hatred to grow. Throw in the toxic world of backstage politics and you've got a simmering pot of sadness for all involved.
Triple H is better than most at the whole 'grudge' thing. That comes with the territory somewhat, him being Vince McMahon's son-in-law and heir, and while Hunter has managed to soften many issues as time goes by, some anger just doesn't scrub, no matter how hard you try.
The wrestling world is full of people who scoff at the mere mention of Hunter Hearst Helmsley, men and women still recovering from a (usually) political battering at the hands of The Game, the Cerebral Assassin, the man who romanced his way into the ultimate position of power in an industry that has an unhealthy obsession with the stuff. Triple H has used his lofty seat to hold many people down over the years, and those many people aren't about to forget.
We all have our reasons for hate. Much of the rancour listed here has understandable roots, from career sabotage to professional jealousy. 'He hates me because I stopped him putting sh*t in Mark Henry's sandwich' might just be the best reason for anything ever, however.