Let's see... the darkest mature point in Nightwing history would be when he let Tarantula shot Blockbuster after he systematically destroyed his life, and was so mentally broken that he couldn't prevent her raping him, and coercing him to marry her.
So... mobster... dark and stormy nights... sexy women with dubious consent... the slaughter of friends... maybe add Scarecrow's hallucination while we're at it since he's in both Bludhaven and Rebirth Bludhaven
Like, noir, but instead of being a grizzled hard-boiled detective, he straddles the line between protagonist and victim
Oh you mean a story I actually want to read?
Hmmh... don't know actually, since I'm not really interested in a mature story...