Frank Shamrock is a legend in MMA. He debuted in Pancrase against Bas Rutten, who would win the Heavyweight title in the UFC, and defeated him by majority decision. By the time he was done in Pancrase he had amassed a record of 11-6-1. A win over Enson Inoue propelled him into a Middleweight (later named the Light Heavyweight) title fight for the UFC against Kevin Jackson. He would submit him with an armbar in just 14 seconds to become champion.
His next fight saw him destroy Igor Zinoviev. In the fight, Shamrock slammed Zinoviev so hard that he broke his collarbone and fractured his C-5 vertebra. He would never fight again but the legend of Shamrock was growing. A couple more submission wins over Jeremy Horn (kneebar) and John Lober (strikes) led into his next UFC fight and the one he called the toughest of his career, Tito Ortiz. From MMA Weekly:
"They all kind of stand out for different reasons. But I’d say my physical, the greatest physical application of martial arts I’ve ever applied, was against Tito Ortiz just because he was so big. It took everything I had in my arsenal of martial arts skills to beat him.
"I’ve had other fights that... fighting Phil Baroni with a blown out knee was like the hardest mental thing I’ve ever done, but physically battling with Tito was just retardedly hard."
Frank Shamrock vs Tito Ortiz is widely considered one of the greatest fights in UFC history. It's sad that the UFC refuses to acknowledge it's significance due to petty issues with Shamrock. This fight was truly his biggest moment. Ortiz was coming off a couple of convincing wins over Shamrock's former teammates in Guy Mezger and Jerry Bohlander. Tito was much bigger than Frank and because of his massive size advantage was considered a favorite despite Shamrock holding the title.
During the fight, Ortiz repeatedly took Shamrock down and worked from inside his guard. Ortiz used his size advantage to score plenty with his strong wrestling and top control but by the 4th round he was starting to slow down. Most of the round was spent with Ortiz in Shamrock's guard after a takedown. With about a minute left in the round Shamrock reversed him and got back to his feet. After an exciting exchange that Shamrock was clearly getting the best of, Ortiz shot in for another takedown. Shamrock tried to lock on a guillotine but couldn't quite complete it. He stood up with Tito grabbing at his leg and delivered a few hammerfists to the side of Tito's head and Ortiz tapped with 10 seconds remaining in the round.
Truly a gutsy and incredible performance. He would retire after the fight and have a falling out with the UFC. Unfortunately, to this day, he doesn't get along with Dana White and he has largely been removed from the history books, at least as far as the UFC is concerned. But it was a great fight and one that should be remembered.