#2. The Undertaker vs Sting
This match is one of those unfortunate scenarios where all stars were aligned at the right place and the right time, but WWE decided to not go ahead with it. Sting made his shocking debut in WWE at Survivor Series 2014. The Stinger helped John Cena's team win a Traditional Survivor Series match, much to the dismay of Triple H.
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At WrestleMania, Sting faced Triple H in a match that saw DX and nWo come out to the ring and interfere on behalf of both Superstars. Triple H won the match in a head-scratching decision and the two Superstars reconciled after everything was said and done. On the same card, The returning Undertaker faced Bray Wyatt and defeated The Eater of the Worlds. WWE could've easily given the fans this dream encounter, but chose not to.
A year later, WWE finally teased the dream match on its official website. This ended up raising fans' hopes, but it was all for nothing. The Undertaker faced Shane McMahon inside Hell In A Cell at 'Mania, while Sting was inducted into the WWE Hall of Fame.