#3 Brock Lesnar
According to Ryan Satin, there is said to be bad blood between Vince McMahon and Brock Lesnar after the two got into a heated exchange backstage after WrestleMania 34. The alleged reason for the incident is that Lesnar went off script during his main event match with Roman Reigns and McMahon was upset at him for it.
Things only got worse however as Brock Lesnar eventually threw The Universal title at Vince McMahon and walked out of his office. In the end, the incident proved just how little Brock Lesnar really cares about The WWE and their top title, but also that Brock Lesnar is only in business for himself and no one else.