#1. Bray Wyatt

TLC 2017 was also supposed to give us the big payoff between Finn Balor and Bray Wyatt as well as the debuts of two new gimmicks for both Superstars with WWE leaning into the supernatural element of both wrestlers.
However Bray Wyatt also had to take time away from the ring to recover from suspected mumps meaning that Finn Balor needed a new opponent for the show. Instead of a battle of demonic entities we were treated to a pure wrestling match between Balor and new opponent AJ Styles.
The build-up to this blood feud between two supernatural entities was met with ridicule at the time with Bray Wyatt's portrayal of Sister Abigail drawing particular ire from the WWE Universe, so perhaps it's a blessing in disguise that this match didn't get to go ahead, especially as we ended up getting the Fiend.
I would've liked to have seen Balor's Demon King persona though. Hopefully there's room for a comeback at some point as I might be one of the few people still interested in seeing a clash of the supernatural between Balor and Wyatt.