#1.) Chad Gable
Jason Jordan had already been in NXT for years, while Gable was fairly newer. However, as American Alpha, they established themselves as the perfect tag team to carry WWE in the future. Their streak saw them get hotter and hotter and it led to a brief NXT Tag Title run. Unsurprisingly, they were called up during the draft for SmackDown, but they were significantly underutilized, despite becoming SmackDown Tag Team Champions.
They eventually split when Jordan went to RAW and Gable was never given the opportunity to live up to his potential. He and Jordan both should have spent a lot more time in NXT than they actually did.