We are know how violent comics can be. Just check out any issue of Punisher (currently drawn by local hero Tan Eng Huat), he'll be blasting the villains to kingdom come. Suicide is not in short supply too. Those old enough will remember X-Men #137 - Phoenix Must Die! Yeah, she killed herself.
But superheroes always had this hang-up about taking lives. One of my favourite Superman story (and also fave Alan Moore story) is Whatever Happened to the Man of Tomorrow? (recently reprinted in hc and way more superior than Gaiman's Whatever Happened to the Caped Crusader?) In that story, Supes felt so bad about taking the life of Mxyzptlk (a demon from the fifth dimension) that he exposed himself to Gold Kryptonite and walked out of the Fortress of Solitude without his powers, supposedly another act of suicide.
Most people have forgotten that when Siegel and Shuster created the Man of Steel, he used to throw people around. And the original Batman by Bob Kane, he carries a gun and uses it with extreme prejudice.
That's why it's so fun to read the 30s superhero reprints by Fantagraphics:
I Shall Destroyed All Civilized Planets and You Shall Die By Your Own Evil Creation by Fletcher Hanks
Supermen! The First Wave of Comic Book Heroes 1936 - 1941
Solid stuff when read together with The Ten Cent Plague and you'll see why the authorities were scared shitless by the comic books. These were wild things.
So forget about the DC Archives, these are the real deal. I suspect these stuff were avoided when DC reprinted 30s/40s materials in those 100-page Adventure digests in the 1980s. Not even a hint when Roy Thomas revived JSA, All-Stars, etc over the years.
Okay, if you want a sample of these hard stuff, go get All Select Comic #1, one of those 70 Years reprints (plus new materials) that Marvel is putting out. The new Blonde Phantom story is pretty lame. (Javier Pulido's art redeems it somewhat) Go straight to the 2 Marvex stories from 1940. They are a riot! (only after that, check out the new Marvex story by michael kupperman)
Marvex kills his evil creators in the fifth dimension. (where else?)
Marvex yanks a bad guy by his hair and says "You are no good! You die!" Death by slamming the baddie against rocks.
"With a mighty heave, Marvex flings the spy right through the wall of the building!"
But the best part:
Girl: "Oh, thank you! You are the only friend I have!"
Marvex: "But remember - we can never be more than friends."
Girl: "Why not?"
Marvex: "Because I am not human. I am Marvex the Super-Robot."
and in another scene,
Girl: "Marvex - you're the most wonderful man I know!"
Marvex: "I AM NOT A MAN - ONLY A MACHINE!"
I think Hal Sharp (listed as the artist of the stories) was worried that readers might get the wrong idea that heavy metal sex was permissible.