#2 Wrestling style
As I'd noted in the beginning of our discussion, this one is bound to get a tad heated! So here goes...CM Punk first rose to prominence on the indie professional wrestling circuit, and then slowly worked his way up the WWE food chain. Now, Punk may not have worked all of his indie career in a life and death "Strong Style" wrestling method such as someone like Shinsuke Nakamura did in NJPW.
However, Punk did push the envelope with the in-ring maneuvers he executed during his run in the indies. Compare his indie stint to his run in the WWE, and one of the most notable differences in his repertoire is that he worked a much safer style in WWE than what he used to in the independent circuit.
The WWE, unlike the umpteen number of indie wrestling promotions, is a global brand, and has a high standard of safety during in-ring performances. Speaking of which, CM Punk, at this stage of his career and life, after having suffered several injuries as well as concussions, would be better suited returning to the WWE rather than wrestling Strong Style high-risk matches in indie promotions as well as companies such as NJPW...