Even in defeat, Brock Lesnar is nothing less than memorable. After a disastrous 1st round loss to highly-regarded striker Alistair Overeem, the UFC's main attraction called it quits -- for good. "Tonight was the last night you will see me in the Octagon," Lesnar told the sold-out Las Vegas crowd. He added (in the third person): "Brock Lesnar is officially retired." On Friday night, the 265-pound heavyweight found himself in the fight of his life after returning to mixed martial arts from a 14 month hiatus. In that time, a second bout with the intestinal disease diverticulitis resulted in 12 inches of his colon being removed. It was a lot to come back from. Too much, it seems.

In Overeem, Lesnar faced an opponent every bit as large (263 pounds at weigh-ins) and just as agile (the Dutchman was a multiple champion in other fight promotions). Friday's fight began with a short feeling-out process. Overeem met Lesnar in the center of the Octagon, where the former WWE star was light on his feet, fainting punches and a couple of kicks. Overeem, on the other hand, stayed low, ducking several of Lesnar's awkward attacks.

As the two engaged, Lesnar bloodied Overeem's right eye. But it had little effect on his opponent. Overeem followed with a succession of punishing knees to Lesnar's mid-section. The knees (honed during his kickboxing career) came one after another, Lesnar visibly shaken. A final kick to the gut sent Lesnar to the ground, gasping. Overeem went in for the kill with a stream of unanswered punches until referee Mario Yamasaki called the stoppage at 2:26 of the first round. The crowd was stunned.

Afterward, Joe Rogan met Overeem in the cage for the obligatory post-fight interview. "Today was all about bad intentions," Overeem said. Happy with himself, Overeem reminded fans that he had promised a first or second round finish, and he delivered. Rogan then acknowledged the Dutchman's next task -- a title shot at champion Junior Dos Santos, who stood waiting in the Octagon.

But a theatrical stare down between the two wasn't in the cards. All eyes were on Lesnar, who was ready for his post-fight interview too. It was then that Lesnar delivered the stunning news. "I've had a really difficult couple of years," he said, referencing his disease and losing his belt in Oct. 2010. He had promised his wife that if he should lose to Overeem, he would retire with a record of 5-3.

And graciously, he thanked his opponent, thanked the UFC and thanked the fans for watching his short but spectacular four-year run in the UFC. His humility was almost unbecoming of a man who prided himself on being "the baddest man on the planet." But in this same run -- which included winning the heavyweight championship after only four fights -- Lesnar has proven to be full of surprises.