What's the opposite word for “sin”?
Well, I have got the answer 'virtue' from most people I asked. But still the answer is not satisfactory to me.
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
If you are asking about sin as a generality (the earth is full of sin), you might consider righteousness or morality.
If you are asking about an individual infraction (that was a particularly heinous sin), I might suggest obedience.