#3 Elias and John Cena
Back during the big Raw 25 show on January 22, Elias targeted John Cena and laid him out with a guitar shot in the middle of the ring. At the time, most believed that this would lead to a match at either the pay-per-view before WrestleMania, or at WrestleMania itself.
The only match between the pair took place on another edition of Raw, but was a triple-threat match which also involved Braun Strowman. They did, however, have a confrontation at WrestleMania 34 - which led to Cena running right through Elias en-route to him being swiftly squashed by the returning Undertaker.
After that though, the WWE just sort of forgot about Cena vs Elias. Luckily for them, the lack of follow-up to Cena's actions at WrestleMania in early April has not hurt the up-and-coming superstar.
The fact that this was completely forgotten about is puzzling, though. Elias would benefit from a feud with Cena in the long-run, not least if he managed to secure a clean win over the 16-time WWE World Heavyweight champion.