Answer: Do not hurt others in ways you would find hurtful.
Explanation: Judeo-Christian principle of the Golden Rule is, don't do to others what you wouldn't want others do to you. Unlike the first option offered, an eye for an eye, which represents the doctrine of the Old Testament, when people took the judgement and justice into their own hands and enforced the law themselves, a Christian doctrine based on peace and love does not imply taking justice into their own hands. As the Apostle Paul said, he who judges another, he is already condemned, so he is also awaiting judgement, which would mean that if we judge others, we have already done something wrong.Today's vocabulary, this could be explained by the concept of karma, which perfectly distributes punishment and blessings according to our deeds, so there is no need to take justice into your own hands.
That is the essence of the Golden Rule of Christian Doctrine, don't do bad to others, if you yourself see that it is harmful or could also hurt you.