@ChristiJunior @EdBoatConnoisseur @jimmybuffettfanaccount @monsterislandcolonizer
I'm not sure why no one (that I've noticed, it's a long thread) has mentioned the Comics Code Authority...but that's the real reason here. Super heroes didn't kill because the writers weren't allowed to show them killing. If they did, their comic would lose the CCA seal of approval, and then stores would either refuse to sell it or risk punishment including vandalism.
This also why American comics became nothing but super heroes despite things like westerns, detective, and horror being very popular in the early days. It's one of the very few genres that could even hope to abide by the code and still sell.