#1 The format of the Men's Royal Rumble

This is a two-sided coin. While one could argue that the unique format of this year's Royal Rumble was a good move by WWE to make it different from other years, the other side is that Brock Lesnar's one-sided dominance went on too long.
Brock Lesnar entered at #1 and eliminated 13 straight superstars - a joint-record in the Royal Rumble. He had confrontations with Kofi Kingston, Rey Mysterio, Keith Lee, Braun Strowman, Ricochet, and most importantly - Drew McIntyre.
He also eliminated John Morrison, Cesaro, Shinsuke Nakamura and many more within seconds. Until McIntyre eliminated him, nearly 2/3rds of the Royal Rumble was a one-sided affair from Lesnar. While enjoyable at first, it quickly wore out. However, we will admit that it led to a great moment when Drew McIntyre eliminated Lesnar - receiving among the two biggest pops of the night.
We were slightly disappointed that we didn't get to see too much of the ring being crowded. It took away from the traditional feel.
Also read: 5 reasons why Edge returned to WWE at Royal Rumble 2020