1. He Has Already Wrestled The Undertaker
The one match that people want to see Sting have more than any other is a showdown with The Undertaker, preferably at a WrestleMania. If it happened it would likely be billed as a "first time ever" match. It makes sense because it would be a big deal, but it's really not the first time they would have a match. They actually had a match in
September of 1990 when Sting was the NWA World Heavyweight Champion. It was a house show that took place at the Greensboro Coliseum in Greensboro, North Carolina when Undertaker was known only as "Mean" Mark Callous. They were actually scheduled for another match at a house show, but that got changed and then Undertaker left the company. It was so long ago that it wouldn't be a surprise if most fans had no idea that this even happened because Undertaker ended up in WWE a few months later in November 1990. He never left while it took Sting 24 years after that match to get to WWE. There's no video of the match as far as we know, but it definitely took place.