Okay, a lot of us don't care for the dark, bleak, bloodier and gorier and nastier direction DC has taken ever since Identity Crisis. This direction, however, only worsened a problem DC has had since Crisis on Infinite Earths -- plenty of death and violence, some of it just for the sake of being 'darker' and 'edgier' and more 'realistic'.
Grant Morrison even pointed out this trend in his last Animal Man issue saying "We thought that by making your world more violent, we would make it more "realistic", more adult. God help us if that's what it means."
However, even in the pre-Crisis DC universe, there are a few incidents that are surprisingly dark for an era many of us now look back on fondly as a brighter time.
There's Professor Zoom's murdering Iris West Allen because he decided that if he couldn't have her, then neither could his foe Barry Allen. Think about it: Zoom was a creepy stalker who ended up stalking and then murdering a longtime supporting character because she rejected him.
And then there's the dark turn Superman and Lex Luthor's feud took in 1983. A decade or two prior, Luthor had become a big hero on another planet, which was renamed Lexor in his honor. The people there all loved Luthor and bought into his anti-Superman propaganda (back then, Luthor was a mad scientist criminal who was in and out of jail much like the Flash's villains, so this was the only way he could be a Villain With Good Publicity until John Byrne's reboot).
This, however, raised the question: If there's this other world where everyone loves Luthor and considers him a hero, why doesn't he just stay there? For a while, the only answer is "Because he's so obsessed with achieving the ultimate victory over Superman". But finally, in 1983, Action Comics #544 had Superman face Lex Luthor on Lexor, with Luthor wearing a new green battlesuit. In the midst of this confrontation, one of Luthor's energy beams bounced off of Superman, and hit a high-tech machine Luthor had been using to stabilise Lexor and keep it from blowing up like Krypton. The energy was then sent into the machine, causing Lexor to explode.
Superman and Lex Luthor were the only survivors. An entire inhabited planet had been wiped out, 'collateral damage' from one of Superman and Luthor's clashes. Fortunately, they didn't just forget about it -- this incident haunted both Superman and Luthor for the next several issues. If I recall correctly, Luthor went off the deep end and tried to destroy Earth before Superman successfully reasoned with him telling him that Earth's the only world he has now and all that.
Still, these scenes are surprisingly dark given how we perceive the pre-COIE era as 'lighter'. But still, back then, perhaps such things were the exception and not the rule (as they are today). And while DC DID do 'dark' back then, they certainly didn't do 'bleak' the way they do now.
Are there any other notably dark incidents from pre-COIE DC that I haven't mentioned?