Brock Lesnar is the biggest star of WWE at the moment. Before WrestleMania in 2004, it had come to the news media that he was going to leave WWE after the match with Goldberg. After which he was very angry on Brock Lesnar. After which it was being speculated that Brock Lesnar would hardly ever return to WWE but he made a comeback in 2013 and today he is one of the biggest stars of WWE.
After John Cena Randy Orton is the biggest star of Modern Day. But in the early days, Vince McMahon did not want to see him in WWE. This was revealed by Jim Ross in the Grilling with JR podcast. During this, he had told that WWE did not want him in the company due to his expulsion from the military. However, even after this, Vince reposed faith in him and today he is one of the biggest stars of the company.