#1 Brock Lesnar

Why so much hate for Brock Lesnar?
Not only is he the single biggest box office attraction in WWE right now, but he is also no doubt that little sprinkle of chaos that adds flavor to the overall product. Beyond that, WWE's move to make him Mr. Money in The Bank was genius and created a situation where the company can keep the fans on their toes in anticipation of when 'The Beast' cashes in.
Did you know a top WWE Superstar just wrestled outside the company? More details HERE
Unfortunately for The WWE, the move was panned by critics as just going back to the drawing board and relying on part-timers to do what a full-time star should be able to accomplish. With that being said, one has to consider that WWE doesn't have many options in a top star right now due to injury and unestablished stars, which makes the pool very shallow.
For example, if WWE were to shoot Roman Reigns up into the title picture right now, the fans would go nuts, so that's not an option. Some might point to Balor being an established star and capable of carrying a brand, his injuries and Vince McMahon's dislike of him as a top guy kind of makes for a bad situation.
In the end, WWE is stuck in this situation right now and will be until a superstar either returns from injury or another one is able to be established. Until then, however, fans could at least accept the product for what it is and try to find the good in it, but they continue to just want to complain instead.