There wasn't even an immediate threat to anyone in that scene, save himself.
But that threat to himself is significant - Nor would have killed him, and so Clark was fighting for his own life. As well, if Nor lived he was a huge threat to other people. So even had Clark's last blow been a "kill", at that point it would still not have been murder. I haven't been arguing that Clark would or could not kill but that he was not a murderer.
So the instinct to "kill" is not there - but the instinct for self-preservation and to defend and protect is there.
It depends, though, on what you believe his primary goal was in that scene. Was it to save the Earth from Nor and his army or was it simply to kill Nor? of course, he knew that he might have to kill Nor in order to achieve his primary goal, and we can only guess about how he psyched himself to do that before hand, although we saw some of that as Ching coached him earlier.
The show clearly established for me that our Clark, maybe because he's more human than in previous incarnations, is capable of rage that will overcome him so quickly that he will take someone's life.
But we never saw any indication in the show of a rage that would lead Clark to kill just for the sake of killing.
c.
