first question: why would an all powerful being have someone kill someone else, seems kind of pointless, he has an infinite amount of power so he could just as easily do it himself (didn't prove you wrong, just the nonsensical nature of what you said).
If God told you to kill someone God'd be facilitating something God said was wrong to do in the first place (according to the Abrahamic faiths) but if God is infallible like the evidence we have now states, then God'd be wrong, which isn't possible.
Still, another question: Which God would've told you this? I wouldn't doubt that in some religions killing another for ritualistic or even righteous reasons was not outlawed, and sometimes embraced. Many ancient cultures used human sacrifice as a way to please the God(s) so maybe you're Incan?
Either way, taking a life, no matter what kind of life plant, bird, human, bug, is morally reprehensible. Everything deserves life, no matter good or evil it's just our jobs as people to make sure that whatever is born, grows up healthy and good natured.
loophole: cloning.
...idk somethin to think about.