Radioactive
Dark Match Jobber
His Ego. He's thought he was the best thing pro wrestling had to offer for over 10 years, when although he's good, he isn't the best and will never be considered the best.
Triple H's battle is internal.
Hes had some great opponents in HBK, Cena, Orton, Rock, Batista, and Austin, but he's never thought anyone was as great as he is. Again he thinks hes the best an no one will ever live up to his greatness
Maybe his ego is pretty huge, but that isn't for you to judge. Triple H (to me and to many others, I'm sure) is the best performer in WWE history. He tops everyone in my opinion, and that's what it all comes down to, just opinion.
But to stay on topic: I think it could be the Rock or maybe HBK. It all comes down to what you enjoyed watching the most.