No resurrections (Phoenix, Green Lantern, Green Arrow, dozens of others), clones (Goodwin/Simonson Manhunter), manifestation as ghosts or demons (Deadman, Ghost Rider) permitted. Dead, and then that’s it, no return. Visits in the afterlife permitted. Costumed superheroes only (Rick Flagg from Suicide Squad doesn’t count).
Lets see…
The Flash (Barry Allen)
Ferrous Lad (LSH)
Kole (New Teen Titans)
Captain Marvel
Goldstar (Booster Gold’s sister)
There are several characters used in one-off appearances that got bumped off at the end of their stories. There’s the really original Supergirl, pre-Danvers, in her orange and green costume from the 1950s, for instance. Or, IIRC, some of the Bizarro Supermen. Although I guess they’re not really heros.
I’m fairly (but not fully) certain Chemical King has stayed dead. If you are going to take current continuity, ever-changing as it is, into account, this is going to be way more difficult.
I think the original Thunderbird of the X-Men has stayed amongst the non-living. He’d be about the only X-Man to manage that.
Now that I think on it, Skin and Synch of Generation X have been dead for a minute or two without coming back. If only they’d been in a more popular book.
An alternate Superboy got pissed off and punched reality so hard that dead Jason got switched with one from an alternate reality where “Robin Lives” won the vote.
Superboy’s reality punches are also the explanation for every retcon and continuity error since Crisis on Infinite Earths. Hawkman? Donna Troy? Doom Patrol? Reality Punch.
I want a crossover with Marvel where Superboy-Prime punches Scarlet Witch, thus destroying all casuality everywhere.
Ted Kord as Blue Beetle was killed in the IC titles and still seems to be dead in OYL canon (there’s a new Blue Beetle, can’t remember his name). But maybe it’s too early to be hedging bets…
I don’t usually join in these comics threads as its been quite a while since I read them…and then I read the more obscure comics from independant studios and such. I remember though a comic series where in the end ALL the ‘super hero’s’ died. It was about a special process that allowed humans to gain super powers (in response to an alien invasion IIRC), but randomly inside of a year they would die…sometimes quietly, sometimes spectaularly (I recall one went up like an atomic bomb…luckily in the midst of an alien horde). I can’t recall the name of the comic now (it was Strike Force something…Moriorty or Moriarty…something like that).
Anyway, it certainly fit the bill as EVERY superhero died in the end. I only read 5 or 6 issues but someone died in every one of them.