The latest victim is Nick Diaz, whose bizarre pre-fight attempts to get into St-Pierre's head were rewarded by a lopsided five-round beating at UFC 158 before 20,145 at the Bell Centre on Saturday night.
"He fought the perfect fight," UFC president Dana White said of St-Pierre.
All three judges scored it 50-45 for the champion, awarding him all five rounds.
St-Pierre's 11th straight win adds to his glittering UFC pedigree. The 31-year-old from Montreal has not lost in almost six years, since UFC 69 in April 2007 (a loss he avenged a year later when he won his 170-pound title back from Matt Serra at UFC 83).
St-Pierre (24-2) celebrated his eighth straight successful UFC title defence, second only to middleweight champion Anderson Silva's 10. He also tied Silva with most championship fights wins (11)
The Canadian also moved into second place in most championship fights (13). And he now holds the UFC record for most championship rounds at 47, surpassing Randy (The Natural) Couture's 44.
St-Pierre upped his UFC career record of takedowns to 84, landing nine of 16 against Diaz.
The 170-pound champion doesn't deliver the highlight-reel finishes some MMA fans crave — seven of his title defences have gone to a decision, after all. But he dominates his opposition, taking them to places they don't want to go.
"He does a great job at taking guys not only out of their game plan but completely out of their element," White said admiringly.
As expected, St-Pierre used his wrestling to control the chirpy challenger, rag-dolling him at times and bullying him on the ground. While St-Pierre dominated on the ground, he did not pass guard as he often does. The champion cited Diaz's slippery jiu-jitsu style and his own fatigue as the fight wore on.
St-Pierre also used his jab and kicks to damage Diaz in the standup game.
Diaz, a talented boxer, came into the fight on the back of two performances in which he landed more than 100 significant strikes — 105 in his UFC 143 loss to Carlos (The Natural Born Killer) Condit and 178 in his UFC 137 win over former champion B.J. Penn.
Against St-Pierre, he managed just 41 while the champion landed 105. St-Pierre led 210-80 in total strikes.
The game plan was to fight at kickboxing range — "All the way in or all the way out," St-Pierre explained — rather than boxing range.
Credit Diaz that he managed to stop some takedowns later in the fight and scored with some punches of his own.
Despite the outcome, Diaz (27-9-0 with one no contest) couldn't resist another jibe.
"This guy has no punching power, no offence, you're a wrestler," Diaz told the champion at the post-fight news conference.
Then he also said: "I appreciate he's a great fighter. He does what he does to win."
St-Pierre may not be a knockout artist, but he won the standup game. Stitches on Diaz's left eyebrow and lumps around his eyes told the tale of a fight in which St-Pierre hit him 40 times in the head in the first round alone.
In spite of the one-sided scoring and statistics, the champion also looked like he had been in a fight. St-Pierre came to the news conference with an icepack for the second fight in a row, explaining he bruises easily around the face.
In fact, the 31-year-old from Montreal looked like someone had rubbed sandpaper over this face. Welts dotted his nose and forehead and his left eye was red and swollen.
Since undergoing reconstructive knee surgery and an 18-month layoff, St-Pierre has fought twice in four months.
He is now headed "somewhere exotic" for a vacation.
"I need to get out of Montreal," St-Pierre said. "I'm going to take a week off and forget about my crazy life for a little bit."
As to the challenger, it's a flight back to the weird and wonderful Planet Diaz.
Diaz had onlookers shaking their heads again after he indicated in the cage after the fight that he planned to retire, only to arrive midway through the post-fight news conference saying he'd like a rematch with GSP or perhaps another shot at Condit.
"I think I can beat you," he said to St-Pierre.
In yet another strange series of monologues, he told the assembled media he hasn't paid any taxes — ever. And that he slept until 8 p.m. fight night because he was confused by the time difference.
Next up for St-Pierre is Jonny Hendricks (15-1), who won a unanimous 29-28 decision over Condit in a wild co-main event that left both men blooded, and with the respect of their boss.
"That fight was unbelievable," said an appreciative White.
Condit and Hendricks earned US$50,000 each for the fight of the night.
Hendricks, who said he broke his left hand in the fight, was promised a title shot if he won.
"Guess what, I earned it," said Hendricks.
White said he had no idea when the Hendricks-GSP fight may happen.
A bizarre fight week saw Diaz skip a public workout, then put on a strange one-man tour de force at the pre-fight news conference that managed to both befuddle and antagonize GSP.
"I never took it personally," GSP said in the cage after the fight.
But at the post-fight news conference, he acknowledged Diaz camp's head games had made life uncomfortable for him.
"I just wanted to get rid of it ... It was very demanding, very stressful," he said.
The antagonism continued right up to the fight with fellow fighter Jake Shields, a member of the Diaz entourage, complaining about St-Pierre's hand wraps.
"I checked GSP's glove and the wrap looked shady," Shields, beaten by GSP at UFC 129, tweeted before the fight.
White said Shields had OK'd the wrap, only to have another member of the Diaz camp come and complain later. The Quebec commission sent them packing, saying it was too late given they had already provided their OK.
Still, there was yelling in the GSP locker-room as the debate continued.
"Everything was about head games, it was crazy," St-Pierre said of the pre-fight buildup.
GSP also responded to Diaz's earlier claim that he was on steroids.
"I never took steroids in my life ... I'm not a cheater, never cheated in my sport," he said.
"You can test me any time, no problem."
How Diaz will fare in drug testing here remains a question mark. The 29-year-old from Stockton, Calif., who has been suspended twice for marijuana, says he smokes the drug medicinally to help social anxiety problems.
The GSP-Diaz showdown was a long time coming. The UFC and former Strikeforce champions were slated to meet at UFC 137 in October 2011, only to have Diaz yanked from the card after failing to turn up for news conferences in Toronto and Las Vegas.
Diaz did his bit to sell tickets for this fight, calling GSP "pampered" during a pre-fight conference call and then failing to show up for a public workout during fight week. He also put on a one-man show during Thursday's news conference, poking away at the champion.
Diaz showed respect after the fight, shaking hands with and hugging St-Pierre, raised his hand above his head. Minutes later, according to GSP, Diaz told an interviewer that the champion hit like a girl and that he wanted an immediate rematch.
"I guess we're back to where we were," said a bemused St-Pierre.
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