After nine years with WWE, CM Punk walked out of the company following January's Royal Rumble pay-per-view. Details as to why Punk departed so abruptly are still up in the air, as Punk has not spoken on the matter at all since it initially went down. Obviously, we won't know the exacts details until Punk or someone close to the situation (presumably Triple H and Vince McMahon) speaks on it, but until then, it's anyone's guess. In his near-decade long WWE tenure, Punk had nearly done it all. A former six-time World champion, the fastest Superstar to win the Triple Crown Championship in history, a two-time Money in the Bank winner and the longest reigning WWE champion of the modern era, the only things Punk had left to accomplish were winning the Royal Rumble and wrestling in the main event of WrestleMania. Even though he wasn't able to accomplish those goals (and he still might), he still had an impressive career, nevertheless. Punk isn't back with WWE any time soon, but one can only assume that he'll be back before long. Whether it be next month, next year or a long time down the road, it's almost a guarantee that The Voice of the Voiceless will return at some point. While he may have seemingly accomplished it all in terms of titles won, there were still a handful of Superstars he had yet to feud with, especially now with the surge of new talent of NXT. Keep in mind while reading that many of these feuds are still very much possible if Punk decides to come back, but if he doesn't, these are 10 ruthless rivalries that we missed out on seeing.