This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / X-Men Origins: Wolverine
When Wolverine's powers first emerged. There's definitely something disturbing about seeing a little kid suddenly growing these sharpish, pointy-looking bones out of his knuckles in what appears to be a very painful process, all while screaming out in pure, unrestrained rage.
As Victor is chasing down young Cyclops, he accidentally emits an enormous energy blast that tears upward all the way through the roof of the school. Let's just hope nobody was injured or incinerated by it.
One from the video game. As Logan slices enemies with his claws, their screams of pain include frantic apologies, shock at all of the blood, and more.
Partly Fridge Horror. When Victor stops Kayla's car, as he advances towards her, he lets his claws rest on the hood of the car, and they tear through it as he drags his hand over it as if it was made of butter than metal. Now imagine such sharp claws on flesh.
Here's another reason to hate this version of Deadpool:
Wade: You whip out a couple of swords at your ex-girlfriend's wedding, they'll never, ever forget it.
It may have been a sick joke, but if not, that's fucked up FAR pass mainstream Deadpool's ally.
Maybe I missed something, but the early part of the movie when Wolverine's with Stryker's crew? That seems to take place before First Class. So it seems possible that Wade did slaughter that wedding party. Really, who knows how much of this movie is still canon or not?