I know they killed Superman and brought him back. Which mainstream DC or Marvel hero type character was the first to be killed off in a comic book, never to return?
That dubious honor may belong to Marvel's Kree character, Captain Marvel. Captain Marvel (Mar-Vell) is a fictional character, a superhero who appears in comic books published by Marvel Comics. The character was created by writer-editor Stan Lee and designed by artist Gene Colan and first appeared in Marvel Super-Heroes #12 (December 1967).
Captain Marvel in his first appearance costume (green and white) and his later retooled outfit where he gained his negabands, cosmic awareness and superpowers in general.
The good Captain was dogged by copyright battles, low ratings, and a lessening of interest, at the time in space-based or cosmic adventuring heroes. Captain Marvel's fan base was small but consistent and Marvel eventually decided to put Mar-Vell out of his misery in one of the earliest graphic novels, The Death of Captain Marvel written by Jim Starlin. Originally published in 1982, this was the first of Marvel's graphic novels and it has been said, quite correctly, that it revolutionized an industry that had started to grow fatally stagnant.
After years of battling various cosmic foes of all size and evil, Marvel finds himself felled by that most human and realistic of diseases. He had cancer and a great deal of this graphic novel examines how his super powered friends react to the death of one of their own from a disease that could have afflicted any of them. Though Starlin allows for a bit of the expected super heroic melodrama, overall the Death of Captain Marvel is distinguished by a quiet, contemplative mood as Marvel deals with his impending death. In the end, its rather touching and truly thought provoking.
Marvel created legacy versions of the character to maintain their copyright including:
- Cross-genetic power transfers - the first attempt to create a legacy/backup for the character came with Ms. Marvel back in the seventies. An accident with alien technology transfers the powers of Mar-vells energy bands to Carol Danvers. Ms. Marvel attempted to bring Mar-Vell's powers to Earth but with little success. The character limped along fighting her main nemesis Deathbird until she lost her powers to the mutant Rogue. She later gained new powers as the hero Binary.
Ms. Marvel's first appearance, her most well-known costume and her overall transformation as a character from 70's hero clone, to independent superheroine to an editorially-confused mess as Binary.
Unrelated characters who happen to take on the same name (and a version of the chest emblem): in Amazing Spider-Man Annual #16, a woman named Monica Rambeau gained the ability to become any sort of electro-magnetic radiation, and took on the name Captain Marvel, apparently unaware of Mar-Vell's existence. By sheer coincidence, her makeshift costume (which becomes permanent) Includes a black "starburst" chest emblem, similar to what's on Mar-Vell's red and blue costume (but with sixteen points instead of eight). She was an Avengers through the second half of the 1980s, chairing the group for a short time. She changed her name multiple times as others become Captain Marvel, going through Photon, and currently using Spectrum.
Genetic descendants - Mar-Vell's lover, the Titanian Elysius, impregnates herself with Mar-Vell's genetic material giving birth to a son, Genis-Vell. While originally going by the name Legacy, Genis bore the mantle of Captain Marvel for fifteen years or so before his untimely death. Interestingly enough, just before his death, he changed his name to Photon (then being used by Monica Rambeau, who was a bit annoyed about having her name stolen twice by the same guy.)
Genetic descendants, part two - Elysius actually impregnated herself with Mar-Vell's genetic material twice, the second time conceiving a daughter, Phyla-Vell (pun intended (genus, phylum)). She may technically have claimed to be "Captain Marvel", but her brother was the one using the name officially at the time. She later took on Quasar's name, and was a part of the mid 2000's version of the Guardians of the Galaxy.
Space-time resurrection using the reality-altering Mkrann Crystal and the Phoenix force, but we the readers already knew it wouldn't take.
Captain Mar-Vell has even been reborn in an animated form as a BLUE Kree and aids the Avengers: Earth's Mightiest Heroes against Ronan and the Kree acquisition of Earth.
The new Captain Marvel (a phrase all too familiar to Marvel's readers) is once again Carol Danvers. After giving her a new set of powers as Binary, she again loses those powers and her Ms. Marvel powers mysteriously return. In a fit of political correctness, Ms. Marvel has now assumed the mantle of Captain Marvel, in a suit that is far less suggestive and more heroic appearing completing the legacy for which she was originally created.
30 years later, the Kree Captain Mar-vell is still dead. And he appears to be and will likely always remain dead, despite his guest appearances, time travel stories and other tricks which always end up with the good Captain returning unceremoniously to the grave.
The first character that comes to mind would be Thunderbird from the X-Men. I am not sure he is the first one but he died way before Captain Marvel (1975 for Thunderbird, 1982 for Captain Marvel).
As for DC, Ferro Lad died in 1967
Rex Cosmos (February 1935 – October 1936)
…if you assume he's not surviving his "comic book death" in which he is overwhelmed by a rush of water.
Issue #1 of New Fun Comics (later titled More Fun Comics) was published by National Allied Publications, which later became DC Comics (this is usually marked as the first comic book for the modern company).
In this inaugural issue, Rex Cosmos is the star of the story 2023: Super Police, which is about a team of interplanetary police officers who protect planet Earth. While he doesn't have any "superpowers", Rex Cosmos reminds me a lot of Marvel's Star-Lord in both his job and his skills, so I think he counts for the purposes of this question.
In More Fun Comics #14 (his 14th apperance), Rex and his sidekick Axel just survived a fall off a cliff because "The draft of air must have broken our fall and pushed us onto this ledge". They look through the underground area and find a river with a boat. As soon as they get in, a sudden gush of water overwhelms them.
And that's the last we ever see of Rex Cosmos. Since the character has never been revived, it's reasonable to conclude that he drowned.
However, the bottom right corner clearly says "Next Issue: The Demented", so the intention likely wasn't to kill him off, especially since he just survived an even worse fake-out death.
Bob Merrit (August 1935 – March 1938)
…if you assume he's not surviving his "comic book death" in which he is shot.
The DC Comics Wikia says that Bob Merrit's superhero ability is "Science", so he is on-par with many of the geniuses of DC and Marvel. His first appearance was in New Fun Comics #5, but he gets shot in More Fun Comics #30 after 24 appearances.
Avoiding the hot twisted cables of the fallen balloons, Bob lands his rocket ship and races towards a —
– lone transport standing at the entrance of the great cave, a group of Asiatics loading in great haste, the last of the stolen gold. As Bob tops a rise the bark of a rifle reverberates and Bob, spinning around, falls—
As with Rex Cosmos, we never see Bob Merrit after this, and the character has never been revived. The bottom right caption merely says "To be continued—", not giving the name of the next issue. While definitely ambiguous, I think it's even more plausible to assume that Bob was fatally shot. Heck, if it lacked those three words, I would say it was a given.
There may be other heroes in these early stories that have more definitive deaths without a "to be continued"; I'm willing to bet it certainly wasn't Captain Marvel in 1982.
One contender is Comet: http://www.comicvine.com/the-comet/29-45912/
DC's new Comet from Redline Comics. The version appearing in Pep Comics #1-17, who was one of the first superheroes to die in a comic, is in the Public Domain.
That was 1941.
He WAS revived, but only in 1960s.