#3 He always generates a reaction
There are very few stars who constantly generate loud vocal reactions from the crowd. Names like AJ Styles, John Cena, Dean Ambrose and, of course, Reigns come to mind.
But aside from Cena, no one gets a more consistent reaction from the WWE Universe than Reigns, which suggests that he has the "it factor" and is clicking with fans in a way that perhaps only a handful of superstars do. If you pay close attention to crowd reactions for both Raw and SmackDown, even some of the biggest stars in the company sometimes hear crickets.
Reigns never does.
That's a testament to the fact that whatever Reigns is doing is working. He makes fans care about what he's doing and who he's feuding with, which, in turns, benefits whoever his rival is at the time. One could argue, after all, that Braun Strowman would never gotten over to the level he's at if it weren't for Reigns, his biggest rival.
The mark of a truly great superstar is that he always makes fans care and passes that on to whatever superstar he is feuding with, which is exactly what Reigns does week in and week out. Why? Because no one generates a reaction quite like he does.