The first and only punch of a boxing match delivered a knockout and plenty of controversy.

Viktor Jurk, 26, landed a vicious left-hook knockout of Edwin Castillo, 23, to open their heavyweight fight on the Karen Chukhadzhian-Paddy Donovan undercard in Mannheim, Germany, on Friday night. 

“Unbelievable,” DAZN play-by-play man Adam Smith said after the strike. “I’m not sure why the referee is counting. It is all over, inside a few seconds.”

One of the fastest KOs ever didn’t sit well with some, as Jurk ignored what appeared to be Castillo looking to touch gloves — a ritual show of respect and sportsmanship — and instead uncorked a brutal punch.

The official time of the bout has not been released as of Saturday morning.

“He was trying to touch gloves and got sucker punchesd (sic),” one X user wrote.

Another added: “he is a real Jurk, looks like he set up Castillo making it look like he wanted to touch gloves…. only to KO him instantly.” 

“He ignored the gentleman tap to put this hook That’s super unfair…,” another chimed in.

Others saw it as Castillo approaching in a relaxed, low and unprotected stance that Jurk just took advantage of to end the bout.

Castillo lay motionless on his back on the mat for a few moments after taking the hit, while Jurk walked stoically back to his corner as the referee began his count,

Wrote on X user: “let his guard down, moved too soft and slow. you’re in a boxing ring not a training ground that’s a big foul play!”

Some on social media even accused Castillo of taking a dive based on the bracing of his fall on the way down, but there is no concrete evidence to suspect any foul play. 

The moment brought back memories of Jimmy Thunder’s famous 1.5-second knockout of Crawford Grimsley in 1997.

Jurk remained undefeated at 14-0 with 12 knockouts, as Castillo dropped to 13-3 with this third loss in his past four fights.