Nunes (16-4) used leg kicks early, shots to the head and body in the middle rounds and a ruthless finishing instinct late to earn a TKO victory over her game-but-overmatched foe. She invited Pennington's fiancé Tecia Torres into the Octagon and claimed that it was the hardest fight of her career due to her friendship with the couple.
Speaking at a post-fight press conference, Nunes criticised Pennington's corner.
"He should have listened to her at that moment", Nunes said.
While Nunes maintained control for the majority of the second round, Pennington was finally able to drag the fight to the ground with about a minute to go, although she didn't do much with it except maintain the position before the fighters worked their way back to the feet a few seconds remaining. The challenger could snatch a guillotine as Nunes tries to take her down.
Nunes made an impression right out of the gate with a leg kick that dropped Pennington and set up the rest of her offense.
But Nunes was never in trouble and continued to attack a tired Pennington throughout.
At no point did the corner afford Pennington one last chance to say she wanted out.
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Amanda Nunes expressed her disappointment in how Raquel Pennington's corner failed to oblige her request to end the UFC 224 main event following the fourth round of action. A Nunes knee appeared to break Pennington's nose and with the result looking like a foregone conclusion, she told her corner that she had had enough.
Despite it being a successful night for Nunes, whose win is arguably going to fuel further talk of a massive Brazilian super fight against Cris Cyborg, it's Pennington's cornermen that have stolen the headlines for all of the wrong reasons.
She showed some signs of a fight back, but Nunes' attack proved to be too strong as the referee stepped into stop the fight midway through the fifth round. She's a fighter, you know? 'If you want to retire you have to fight me first'. This was very hard for me.
"I kind of think that if it was a male fight, it wouldn't be such a hot topic of discussion".
Immediately after this exchange happened, though, many of those watching (including UFC fighters) took to social media to declare it appalling.
"I live in the USA, but I'm from Brazil and I represent Brazil with the flag and my belt", Nunes told the crowd after her sixth straight win.
Former Brazilian jiu-jitsu world champion Mackenzie Dern continued her winning start to life in the UFC with a first-round submission finish of American Amanda Cooper, though the grappling ace clearly has issues with her preparation - she missed weight by a colossal SEVEN pounds at Friday's official weigh-ins.