#1. Roman Reigns vs Goldberg

The way the entire situation between Goldberg and Roman Reigns was handled was quite questionable. For one, Reigns earned a Universal Championship match at WrestleMania by simply telling Goldberg "I'm next!", while Drew McIntyre had to scratch and claw his way to Brock Lesnar.
Even if you leave that aside, you could argue that it was a match big enough to sell itself - which is most definitely true. However, Reigns was abruptly pulled from WrestleMania 36. The first rumors suggested that he was pulled as he felt ill during the tapings, but Reigns trashed the rumors, stating that his wife Galina Becker is pregnant with two twins. While he didn't outright admit that it was the reason he pulled out, it was implied.
WWE replaced him with Braun Strowman and gave no prior explanation. They simply announced that it was going to be Goldberg vs Strowman and The Monster Among Men benefited by winning his first Universal Championship.
What was even weirder is the fact that WWE has stopped acknowledging Roman Reigns altogether. They've even removed him from Make-a-Wish video packages, A WrestleMania 31 video clip, and more, with the commentators reportedly instructed to avoid mentioning his name.
This is the only feud on the list that didn't have a match...yet.
Becky Lynch has been challenged HERE.