Yes, this was another one of those grey areas for Clark that I'm sure for which he'll do many a night patrol in penance. While Johnny Corban was a man, Metello was a monster, whose mere existence was deadly to Superman. However, was Metello any more an of a menace than if someone had gotten Clark's powers and used those powers for self-gain? Did Clark given up on Corban's redemptive ability too soon or did he see him as a lost cause? One could even argue Wiliam WW Walldecker / Resplendent Man used his new powers unwisely. Did the Vale brothers kill Corban or did Superman when he disabled him? Did he think that what he was doing was more humane than allowing the Vale brothers to use Metello as their own personal Frankenstein? Yes, these issues certainly would bother Clark. He doesn't like to have to make life and death choices, because he believes that power should only belong to a higher power. Seeing Lucy's anguish over losing her boyfriend (despite him being a lousy boyfriend at that) I'm sure will pain Clark's gut for a long while to come.
Also, not one of my favorite episodes, but you got right to the heart of the matter in your story.
