#4 Bobby Lashley costs Brock Lesnar the Universal Championship
Yes, we do realize that Lashley is feuding with Elias at this moment. However, everyone in WWE definitely realizes that they need to get a Lashley vs. Lesnar feud in before Lesnar leaves for the UFC in due time. What better stage to plant the seeds of this rivalry than at the Greatest Royal Rumble? This could be a blood feud that stretches across months.
This could also be a great way to put the title on Roman Reigns but leave the audience with a moment that is so shocking that they don't boo the match like at WrestleMania 34. Pretty much like how WrestleMania 31 ended with Seth Rollins cashing in the 'Money in the Bank' briefcase. This would allow Reigns to move on to other opponents such as Samoa Joe.
Lashley has claimed that fans have hounded him about facing Lesnar for many years now. His MMA credentials and his achievements outside WWE make him a worthy contender.