Ethics: What makes an action good?

A college-level course could be spent on the topic of "What makes an action good?" What I'd like to do here is give a simplified overview of the main ways that question has been answered, and then make a few follow-up comments.
Q: So: What makes an action good?

1. It fulfills or harmonizes with natural law. (Natural Law)
2. It fulfills an essential moral duty. (Deontology)
3. It will achieve a good purpose. (Consequentialism / Utilitarianism)
4. It is the outward expression of inward virtue. (Virtue Ethics)
5. It fulfills a divine command. (Divine Command Theory)

There's nothing preventing an action from being "All of the above". First, a quick survey of some potential problems of each approach:

1. Natural Law is limited in that all kinds of human actions are not necessarily associated with some sort of immutable natural law. Also, emphasis on some natural laws -- notoriously, "survival of the fittest" -- can lead to some brutal results.
2. The "essential moral duty" begs the question of how we know what that essential moral duty is, and why exactly those duties are good.
3. The utilitarians are the ones for whom "the ends justify the means". It is the only theory that bets everything on being justified by a future outcome. There is a blind spot in that we don't know the future, so the true consequences of an action are not actually known in advance. There is no safeguard against causing all kinds of actual harm in the name of good intentions and hoped-for results. Also, there is such a thing as a method that sabotages its intended goal; that risk is typically not recognized.
4. The outward expression of inward virtue begs the question of what exactly is virtue and why exactly is it good. It has nearly the opposite risk compared to the utilitarians, in that for the "virtue ethics" view, the end result is, in practice, nearly irrelevant. In its weaker moments, it tends toward narcissism; it has a self-congratulatory streak.
5. The "divine command" theory presupposes a way of knowing God and a way of knowing his will. Beyond those hurdles, it then bets everything on the character of God. If God is not actually intrinsically good, then "divine command" is not necessarily intrinsically "good" either. (This last point is not at all academic. Not all religions hold that God / the gods are always intrinsically good. According to some religions, God / the gods may not act out of goodwill or virtue.)

But it is plain that there is a lot of overlap between the different approaches:

1. Natural Law has roots in the real world around us. If we look for what harmonizes with nature, what makes the natural order grow and flourish, then working according to natural law is also working for a good end, but with better quality control over the means employed to reach those goals.
2. The "essential moral duty" could coincide with nearly any of the others. the "essential moral duty" is a blank list waiting for someone to fill it with its vision of what is moral, essential, and obligatory.
3. The utilitarians provide a useful foil for the "virtue ethics" view, insisting that we consider the results of actions.
4. Likewise the "virtue ethics" perspective is a useful check-and-balance against utilitarians, noticing that some methods are not consistent with the good intentions that are the stated goal.
5. If God is the creator, then "divine command" may largely reflect natural law, in the sense of aiming for what makes the natural order grow and flourish.

From a Christian point of view, the theories largely coincide. As a list of considerations, they are to be weighed together, not separately; any separation amongst them is a warning sign that something vital has been overlooked. In Christian ethics, all the ethical theories are bound together by Christ's teaching of the highest good: Love of God, love of neighbor; some would also say by the Genesis account of creation being inherently good. On this view, the objective reality that grounds all of our ethical decisions is the goodness of what God has made. From there, love of what God has made is the natural law, the essential moral duty, the driving force that motivates and identifies good results, the definition of real virtue, and the content of divine command.