In June 2002, Lesnar won the King of the Ring tournament, defeating Bubba Ray Dudley in the first round, Booker T in the quarter-finals, Test in the semi-finals and Rob Van Dam in the finals, earning him a shot at the WWE Undisputed Championship at Summer Slam. After a quick feud with Hollywood Hulk Hogan in August 2002, Lesnar defeated The Rock at Summer Slam on August 25 to become the new WWE Undisputed Champion and youngest WWE Champion at age 25, a record previously held by The Rock himself.At Vengeance on July 21, Lesnar lost to Van Dam in a WWE Intercontinental Championship match by disqualification. At the time, the WWE Undisputed Championship was being defended on both brands, so Raw General Manager Eric Bischoff expected Lesnar to return on Raw the following night. General Manager Stephanie Mc Mahon announced that Lesnar was only required to defend the title on Smack Down!Lesnar's first feud was with The Hardy Boyz and Lesnar defeated Jeff Hardy by knockout after Hardy was unable to respond to referee Theodore Long at Backlash on April 21, his first official televised match.
Leading up to the match, in the storyline, Lesnar broke The Undertaker's hand with a propane tank.In November 2008, Lesnar defeated Randy Couture to become the UFC Heavyweight Champion.Shortly after a successful title defense in a rematch with Mir, Lesnar was sidelined due to diverticulitis.This led to Lesnar turning face for the first time.In order to gain his revenge on Big Show and Heyman, Lesnar interfered in his first title defense, which came against Kurt Angle the next month at Armageddon on December 15, where Lesnar executed the F-5 on Big Show, which enabled Angle to win the WWE Championship. , however, Angle introduced Heyman as his manager and, despite promising Lesnar a title shot earlier in the evening, declared that Lesnar still would not get it.In June 2016, at UFC 199, the UFC announced that Lesnar would return to fight at UFC 200 even though he was still contracted with WWE.