Last year, it was easy.
As the world's combat sports writers convened at this time in 2020, there was only one fight in the discussion for which the result could have been deemed KO of the Year.
Not only was Joaquin Buckley's spinning leg kick erasure of Impa Kasanganay the top knockout of those 12 months, but it also remains one of the single best in mixed martial arts history.
Which means 2021, by definition, is a bit more challenging.
Not that there weren't spectacular, highlight-reel finishes. In fact, there were several.
Among them, a single Derrick Lewis uppercut that left Curtis Blaydes stiff as a board. A flying Cory Sandhagen knee that rendered Frankie Edgar similarly motionless. And a precise spinning elbow from Jiri Prochazka that sent Dominick Reyes tumbling face-first to the canvas.
All were both intensely violent and combatively beautiful at the same time.
But when it comes to breaking ties, there's something about significance.
To end a fight in dramatic fashion on the grandest of stages and under the brightest of spotlights is an ability left to the best of the best in the MMA world.
And given that criteria, there was none better in 2021 than Kamaru Usman's KO of Jorge Masvidal.
The UFC's reigning pound-for-pound kingpin defended his welterweight crown with a sudden, devastating impact atop a pay-per-view show against a high-profile opponent in the company's first fight card with a capacity crowd in more than 13 COVID-19-riddled months.
When it was over, Masvidal's left hand dangled limply in the air.
But it was the only part of his body still moving.
The perpetually chatty Miami-based welterweight was all but vaporized by a single right hand from Usman, cutting short their highly anticipated title rematch just 62 seconds into the second frame of a scheduled five-rounder in the UFC 261 main event.
"Wow," Masvidal mouthed to himself, shaking his head as Usman's hand was officially raised.
Upon further review, his exclamation was apt.
"Jacksonville, Florida, you all said you wanted violence. You're welcome," said Usman, who was defending his belt for the fourth times since winning it in March 2019. "I told everyone I'm still getting better. The sky's the limit for me."
It was a far cry from the mat-heavy first dance between the two, won by Usman via unanimous decision nine months before in Abu Dhabi. This time, Usman fared just as well with his hands, though he did get Masvidal hard to the mat about halfway through the opening round.
Masvidal, the crowd favorite in Florida, was a bit more active to begin the second round but was still taking the cleaner and more noticeable shots from Usman. When the decisive right landed, he fell to his back and took four more glancing ground strikes before Herb Dean could intervene.
The fighters embraced in the cage afterward, and Usman said the rivalry fueled him to work harder.
"You elevated me," he told Masvidal. "It's been a while since I've been extremely nervous for a fight.
He continued: "Coach kept yelling at me and telling me: 'Stay with the fundamentals. Stay with the fundamentals.' With my fundamentals, I am the best pound-for-pound fighter on the planet."
Masvidal, who had never been finished in the UFC and not at all since 2009, was gracious in defeat.
"First time in my career I've been knocked out like that, and it's in front of all my friends, my family and my people," he said. "That's what happens when you get too overconfident.
"He won this fair and square."