https://m.imdb.com/title/tt5864950/

A user on the Femaledom forums found a halfway decent horror film scene featuring the castration of a prisoner by some kind of large, male horror creature. Minute 36:30 - make sure your pop-up blockers are up to date and active.

For those of you who don't visit the link, I'll describe the scene - reading the concept in words is often more titillating than viewing the active scene. 

An effeminate figure is on the floor of a dimly lit basement/dungeon, face down and moaning. Standing over is a large, male human form, wearing a demonic leather mask, a leather apron, and a monstrously proportioned black dildo. 

The monster bellows, stoops to it's knees, and proceeds to violently enter and rape the now screaming person on the dungeon floor. Other crazed onlookers - all unkempt, disgusting looking monsters in their own right - laugh and cheer at the carnage as the dildo does it's damage. Blood begins to spatter the floor as the monster violently pumps his weapon.

After the monster tires of his game, he flips the moaning, crying figure over and we see that he has male genitals hanging between his bloodied legs.

The monster reveals menacing leather gloves, adorned with spikes and wicked metallic claws. It plunges the claws into the scrotum of the man on the floor, who screams anew at this vicious assault on his testicles.

We are treated to a montage of sorts of the room - evil figures cackling and screaming with glee, the monster roaring, twisting and pulling on the testicles as blood sprays, and the masked man on the floor flailing and screaming.

After a few moments, we see a blob of misshapen organ fall between the man's legs onto the dingy floor. Is it a shred of cock? A crushed testicle? It's hard to tell, but the gore is appreciable nonetheless. 

The monster, with one final roar, rips the scrotum from the crotch of the man, who has passed out. We get a few frames of severed scrotum, plump with testicles and jagged tear line visible, sitting in the palm of the monsters gloved hand. He squeezes the nutsack a few times, then tosses it to the floor with a splat.

As far as horror movie props go, it's pretty well done. The props are a bit plasticky, and the framing of the scene fits the "campy" horror genre that is expected. 

For those who enjoy the idea of being assaulted, testicles crushed and ripped from our body -- it's a pretty good scene.