#4. Nick Diaz vs. Georges St-Pierre – fought at UFC 158

Former UFC welterweight champion Georges St-Pierre’s rivalry with Nick Diaz came to a head at UFC 158. It ended up drawing one of the biggest pay-per-view buyrates in the promotion’s history.
It was hardly a surprise. The two men seemingly despised one another, with GSP’s clean-cut, respectful reputation clearly galling on Diaz, who was convinced that the nice guy persona was an act.
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When St-Pierre defeated Diaz via unanimous decision, though, it looked like the feud would be over. Unfortunately, that simply wasn’t the case, and the two men, primarily Diaz, continue to snipe at one another to this day.
Months after the fight, Diaz claimed that GSP cheated at UFC 158 by not officially making weight and using performance enhancing drugs, something that was never proven.
It’s a story Diaz has largely stuck to ever since. In 2019, when St-Pierre officially retired from MMA, Diaz again labeled him a cheat. He also claimed that the Canadian “fought like a b*tch” in their clash.
Naturally, St-Pierre has been more respectful, stating in 2020 that Diaz could still be a UFC champion if he were to return to the sport full-time.
However, he has also stated that he never made peace with the Californian, suggesting that he too may still hold a grudge of sorts against his former foe.
#3. Michael Bisping vs. Vitor Belfort – fought at UFC on FX 7

During his fighting career with the UFC, Michael Bisping was renowned for building grudges with his opponents, even the more mild-mannered ones. The former UFC middleweight champion became one of the promotion’s biggest villains during his prime due to this tendency.
However, for the most part, whenever Bisping faced off with a rival in the octagon, he would bury the hatchet with them after the fight.
Even Luke Rockhold, who had a bitter rivalry with ‘The Count’ that spanned two fights, was recently pictured training with the UK native. It showed that the bad blood between them was gone.
However, Bisping has always held a grudge with former opponent Vitor Belfort, who knocked him out in January 2013 in a UFC headliner. The reason for this is largely understandable. The same head kick from Belfort that stopped Bisping essentially wrecked his career. He suffered an eye injury that still affects him to this day.
That would be bad enough, but Bisping has always stated that he feels Belfort was cheating during the fight due to his use of testosterone replacement therapy. And recently, the grudge came back to the forefront when Bisping spoke out about Belfort’s upcoming boxing match with the legendary Evander Holyfield.
‘The Count’ stated that he “hopes Evander batters him." He said that he’d take great pleasure in such a thing happening, while also labeling Belfort a “piece of sh*t.”
Evidently, this is one grudge Bisping isn’t willing to let go, despite their fight happening over eight years ago.