3 times developing a heel persona worked for UFC fighters and 2 times it didn't

#2. Didn't: Frank Mir's heel turn

Frank Mir is a legend in heavyweight MMA. Whenever there are conversations about the best grapplers above 205 lbs, he's often held in high regard alongside Fabricio Werdum and Antonio 'Minotauro' Nogueira. Not only is he a legend, but he is a former UFC heavyweight champion.

Mir was scheduled to welcome Brock Lesnar to the UFC at UFC 81. He introduced the heavyweight division to a level of trash talk never seen before.

First, the Ricardo Pires Brazilian Jiu-Jitsu black belt subjected Lesnar to a stream of ridicule. He focused on his foe's relative MMA inexperience and past as a professional wrestler. Lesnar fought Mir to the best of his abilities, securing takedowns and vicious ground and pound.

However, after being docked a point for striking Mir on the back of the head, he was caught by a kneebar. The then former WWE Superstar was forced to tap out. After Lesnar rebounded from the loss to set up a hotly anticipated rematch at UFC 100, the two locked horns. This time, Mir lost after yet again subjecting his foe to an avalanche of trash talk.

Even after the loss, the Syndicate MMA fighter continued his verbal onslaught. He went so far as to claim he hoped to break Lesnar's neck. He hoped the latter would become the first fighter to die due to injuries suffered in the octagon.

The heel persona was ultimately unsuccessful. It didn't transform Mir into a bigger star or cause fans to tune into his fights more than they already were. Furthermore, he never recaptured the undisputed heavyweight championship that he once held prior to his heel turn.

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#1. Did: Chael Sonnen's heel turn

Chael Sonnen was, in many ways, a precursor to Colby Covington. Like Covington, Sonnen was an NCAA Division I wrestler whose low finishing rate did not endear his fighting style to fight fans across the world. Similarly, both began their heel turns with vicious promos targeting the nation of Brazil.

The former middleweight and light heavyweight first challenged Anderson Silva for his UFC middleweight championship at UFC 117. During the leadup to the bout, Sonnen subjected his foe to a heated onslaught. He even swore he'd retire Silva who, by then, had ruled the middleweight division for four years.

While Sonnen ultimately lost, the event drew 600,000 PPV buys, and the American became a reliable PPV draw for the UFC. The next event he headlined was UFC 148, which featured his rematch with his Brazilian nemesis.

Again, Sonnen defined the leadup with vicious trash talk. He joked that he'd slap his foe's wife on her rear and have her cook him a medium rare steak. The title challenger took his heel work to such an extent that he attended press events wearing a t-shirt commemorating that particular line. Unfortunately for the American, he failed to capture the middleweight championship from Silva.

His heel work still yielded success as UFC 148 drew 925,000 PPV buys. His popularity as a heel paid off. Right after his defeat to his Brazilian rival, Sonnen's trash talk earned him a title shot. It was in a weight division above against Jon Jones at UFC 159, drawing 530,000 PPV buys.

Prior to his heel persona, no one paid any attention to Sonnen. Afterward? He remains a household name in MMA despite his retirement.