The conclusion to the The Death and Return of Superman video is that DC, by killing and reviving Superman, "broke death". By which they mean that other titular characters who died subsequently were not permanently dead, they came back to life through one literary device or another (hidden power, alternate universe replacement, altered timeline, cloning, reincarnation passing of the mantle/costume to another, etc.).
Both DC and Marvel have done this countless times. But I suspect that Superman was not the first. So, who between DC and Marvel broke death first, and with which character? For the sake of argument, let's say Elseworlds, What If's, and other "one-shot" don't count.