There's also "implied darkness", and sometimes that can get overshadowed by seeing explicit darkness. Now, implied darkness can be seen in a lot of things, even kids' shows, and one might not notice it until later (or in some cases, when you're older and more mature to realize).
I find implied darkness to bring about more "what if" statements or more room for interpretation. It gives key statements and actions that are questionable in the settings, but well placed in a way where it can also pass a radar (say, television broadcasting).
Take for instance 1969's Scooby-Doo, Where Are You?.
There have definitely been moments where the villains in the show actually tried to kill the gang so that they couldn't find out what they were scheming. Of course, when we're kids, we're all focused on figuring out who's under the mask. But as we grow older, these little hints and implications appear.
I think one instance for me was when Velma had been tied to a wooden slab by the Yeti Monster and placed on a conveyor belt to a running saw. Scooby-Doo had to act quickly and get her out of there.
My first reaction as a kid: "Oh no!! Scooby-Doo, save her!"
But when I get older, my second one was "Woah...this guy was so money-hungry, he was willing to kill someone so that they didn't find out and tell authorities."
That there is implied darkness. It's the bits and pieces that leave room for implications as opposed to straight telling it like it is.
For me, that's always a bit darker