#1 Brock Lesnar
Vince McMahon has often been accused in recent years of depending too much on Brock Lesnar and putting the world title on him repeatedly. There's no denying that Lesnar is one of WWE's biggest attractions and Vince McMahon relies on him for major occasions.
As described in Brock Lesnar's book Death Clutch, Lesnar decided that he was done with WWE in 2004. Weeks before WrestleMania 20 where he was scheduled to face Goldberg, Lesnar told Vince McMahon that he wanted to quit. Lesnar did leave after WrestleMania 20 but not on good terms with Vince McMahon.
Another recent incident took place after WrestleMania 34 where Lesnar retained his Universal Championship against Roman Reigns in the main event that was highly criticized by the WWE Universe. Lesnar came backstage and angrily threw the title on Vince McMahon, who shouted back with expletive words. Ryan Satin reported the following about the incident:
"We’re told Lesnar was livid when he returned to the backstage gorilla position and went off on the WWE Chairman … who was not happy about it. We’re told there’s a belief that Brock may have gone off script a little bit near the end of the match, but we’ve been unable to confirm if this is true."
It was reported last year that Brock Lesnar's contract with WWE has expired. However, the belief is that Vince McMahon will call him back in time for WrestleMania 37. As per reports, the plans are for Lesnar to face Drew McIntyre and Keith Lee in a triple-threat match at The Show of Shows.