I think DC is truly darker in a sense of how DC comics initially portrays their characters and universe vs how Marvel portrays theirs. Especially in their cartoons and live action shows.
Whether we’re talking about hypersexualization of female characters in comica or openly depicting violence and more mature themes like prostitution in tv shows, DC has done it - while Marvel hasn’t really touched on that sort of issues.
I can’t help view Supergirl as somewhat of being a intergalactic victim to hunan trafficking when she was the leader of the female furies. She may have went willingly but the point is that she was brainwashed and other things. It’s no different of how young girls get selected and tricked into prostitution.
Barbara Gordon being shot, undressed and taken pictures of nude in The Killing Joke. Violation is a pretty mature topic that Marvel wouldn’t dare to touch.
Harley Quinn being re-invented for the Arkham series, wearing a gothic maid outfit to appeal to a younger audience, likely teenagers who are heavily into anime.
I still remember watching Titans and on the last episode when Dick goes back to Gotham, well at least in his head, we see a hooker making sexual contact with a man in the alley, though brief, it’s still there.
I’ve seen alot of Marvel, but never have I see them being so dark, daring or mature as SC in these types of ways.
As far as straight up darkness, gore and violence in tv shows, Gotham is far more violent than say The Punisher or Daredevil. You see things like torture and people getting limbs hacked off in realistic manners for filler.
But I guess these days, maturity can be arguable - in other words, what one person views as a dark topic, another person will make into a joke or make light of it. It’s 2019, anything can happen.