There are hundreds of them (just search by hashtags in the posts above). Of course same set of videos/pics repeated over & over, but my point is that such stuff is present all over Twitter & FB and anyone accessing those platforms can stumble upon them. Twitter doesn't even seem to put them behind a "Violent/NSFW" click-through.
I don't see how nudity can be more damaging or pernicious than such content.
I'd suggest starting with 'Law abiding citizen' and 'John Wick'. Note that an 'R' rating means that children under 17 are not allowed to watch these without a parent or a guardian present. But that's different from 'adult-only', after all, technically it is still allowed. The proper marker would be 'X' if it was to be compared to 'adult only'.
Warning, extremely disturbing content:
I'm not sure of the "kids will suffer because of violent images" idea tho, we were shown a crap ton of terrible imagery from WWI/WWII/Holocaust/Vietnam when I was in middle school, and if anything I thought it was a good thing.
For the first link I see this: "The following media includes potentially sensitive content. Change settings"
I don't have an account, so you may have changed your settings