Fares Ziam delivered one of the UFC’s most “insane” knockouts ever on the undercard of the Fight Night event in Paris on Sunday (AEST).

The “Smile Killer” left Matt Frevola out cold and MMA fans stunned, as The Sun reports.

Considering how chilling the finale was, it’s incredible Ziam (16-4 record) has never triumphed inside the distance before.

One UFC fan labelled it “one of the most brutal knockouts I’ve ever seen”.

After 13 minutes of their lightweight contest in Paris, home favourite Ziam put a forearm around Frevola’s head to hold it in position and thrust a devastating knee into his face.

The American crumpled to the ground immediately, prone and not moving a muscle.

Ziam went in to finish the 34-year-old off, but there was never any doubt it was already over.

And the referee darted in to pull him away from the New Yorker.

“Frevola was out, holy f**k that’s scary,” responded one viewer.

Another posted: “KO of the year contender?”

Ziam won 10 of his 12 MMA bouts before switching to UFC five years ago.

Since then the 27-year-old has come out on top in six of his eight fights.

That includes a remarkable success seven months ago, in his last bout before taking on Frevola.

Peruvian Claudio Puelles put him down no less than seven times, but Ziam still notched a split-decision victory after landing more strikes.

He was then into the third and final round against Frevola when he produced his first “finish” – namely winning without needing to go all the way to the scorecards.

Frevola long ago graduated from the University of Tampa with a degree in Criminology.

But he won’t need his academic background to concur with one fan’s verdict that Ziam is a “bad man”.

However, some viewers were unhappy Ziam tried to land more quick blows after Frevola was knocked out.

One fan even suggested: “He should be disqualified for those two punches afterwards. It was clearly a knockout.”

Apart from the late blows, many fans loved the action.

“This is absolutely nasty, wow,” one wrote on X.

“Absolutely enjoyed this fight from start to the amazing finish,” wrote another.

“Bro he might be dead,” added a third.

Thankfully the 34-year-old Frevola (11-5 record) was able to recover and has now been knocked out in consecutive fights.

In the main event of the evening, Brazil’s Renato Moicano ruined the French party by forcing a doctor stoppage in the third round of his clash with Benoit Saint Denis.