The hardest-hitting fighter in the UFC punches a man in the groin in the new 'Jackass Forever' movie

• Francis Ngannou is the hardest-hitting athlete in UFC history.
• The MMA heavyweight took those skills to strange levels when he whacked a Jackass star in the groin.

Francis Ngannou is the hardest-hitting athlete in UFC history, according to the mixed martial arts firm itself.

The heavyweight champion retained his title Saturday while exhibiting skills secondary to his striking, such as a wrestling prowess that kept challenger Ciryl Gane at bay through the five-round fight.

But Ngannou showed in a new movie that he remains a puncher at heart, by whacking an actor in the groin.

Paramount Pictures aired a scene from the upcoming "Jackass Forever" film, which is released in US cinemas from February 4, on YouTube earlier this month.

The clip features Jackass elder Johnny Knoxville explain that they duped cast member Ehren McGhehey into agreeing to take a low blow from an elite fighter by convincing him that the athlete throwing the shot would be a lightweight.

Little did McGhehey know that it would, in actual fact, be a hulking heavyweight who is almost 100 pounds heavier than those who compete at the 155-pound limit.

Ngannou can be seen warming up, throwing practise shots at a heavy bag, before aiming a punch at an area that is, let's just say, not where you want to be punched.

Watch it here:

The force from Ngannou's shot left McGhehey crumpled in a heap on the floor, with a mouth aghast at the agony.

McGhehey is seen in the clip reflecting on the punch, and even smiling about it, so it seems as though the punch did not cause any lasting damage.

As for Ngannou, the fighter looks set to rehabilitate a knee injury that he took into the Octagon for the UFC 270 victory over Gane.

It is unclear if he'll ever compete in the UFC again as he could soon test free agency, or seek a crossover boxing match involving Tyson Fury.