Batman was not really "Dark" until the 80`s and Frank Miller.
His first story in
Detective Comics had him breaking mobsters' respective necks by hanging them from bannisters and light fixtures. Subsequent issues had him doing things like hold a smoking gun and cocking the hammer, and running a Nazi sympathizer through with a sword. Even Robin was introduced blasting away with a Lewis machinegun.
Getting his own book toned
him down just a little... by introducing Catwoman, The Joker, and Clayface. And Bruce in his civilian ID was an asshole even by the standards of the day. (A full-force birthday spanking for the kid who saved your life at least three times by then, seriously?) It took Mort Weissinger taking over the character in the Early '50s to turn him into the campy cardboard cutout of the '60s TV show.
If not for Batman, the likes of Shadow, Green Hornet, The Spider of Gotham, The Face, or some similar business suit, trench coat, fedora, and mask mystery man captures the public imagination. And DC promotes Green Arrow and Wildcat more. We may even see a Silver Age revival of the latter with a Barry Allen treatment.