Ultraman kills “a” Superman – Adventures of Superman: Jon Kent # 1
Earth 3 villain Ultraman shows how much he hates Superman regardless of where that may come from in the pages of DC Comics’ Adventures of Superman: Jon Kent.
It was revealed later in the story that Ultraman has developed a machine that weakens Kal-El to a degree that Ultraman can beat him up. This is the reason why he manages to get the drop on this Earth’s Superman and has been doing so before the start of the issue.
Ultraman then snap this Superman’s neck…
And proceeds to disintegrates this alternate Clark to dust with his heat vision.
This sets the stage for the eventual fight between Superman Jon Kent and Earth 3’s Ultraman.