ACTION COMICS 374 (March 1969)--2nd story, "No Mercy for Supergirl" by Leo Dorfman and Kurt Schaffenberger:
The Stanhope Sensation is captured by an alien who calls himself the
Avenger. In another galaxy, on the planet
Sarkon, his people follow a strict no-kill policy. Nothing that is alive may be killed not even plants or insects. Anyone who dares to kill is sentenced to the
5th Continuum--a realm more dreadful than the Phantom Zone. The Avenger and all his people are super-beings and they have decided to extend their no-kill law to every super-being in the universe.
Because the Avenger had observed Linda cutting a flower and preserving a butterfly, she has killed and therefore must be condemned to the 5th Continuum. Stalling for time, Kara asks the Avenger to accompany her to the Congo, to the abandoned lab of the late Dr. Carney, who was working for the W.H.O. to cure jungle fever. At the lab she asks the Avenger to light a candle. Then the Caped Kryptonian shows the alien that a test tube above the candle held deadly microbes which were all destroyed by the heat of the candle. Therefore the Avenger has committed murder.
As the Avenger holds himself to a higher standard, he does not condemn himself to the 5th Continuum and instead uses his self-destruct button, dissolving into a cloud of atomic particles.