After two thousand years ethics, philosophers have distilled ethical theories into three basic types: virtue theories, rule-based theories, and consequentialist theories. I shall show where the philosophers we have studied fit into this scheme, then discuss other views which I regard as anti-ethical.
Virtue theories are primarily theories about the good person. Aristotle considered human excellence in the guise of contemplation and the moral virtues to be the highest good for a human being as such. This view came under some criticism by the Medieval Christian Philosophers, on the grounds that it does not take into account the highest good, the relation of the individual to God. On the other hand, it could be argued (as with Augustine) that the heart of Christian Ethics is love, which could be classified as a moral virtue. The "ethics of ambiguity" advocated by Simone de Beauvior is, on my reading, closely related to virtue ethics. Although we are said to make our own values, the conditions for so doing (courage, patience, etc.) correspond to the moral virtues.
Rule-based theories are about actions, a good act being one which conforms to or is done out of observance of a rule. Kant's theory is clearly rule-based, where the relevant rule is a principle that can be made universal. Theological ethics can also be rule-based: the right act is one done in obedience to the law of God. Pure rule-based theories base rightness in an original law, say one prescribed by reason itself (Kant) or by a superior being. Derivative rule-based theories base it in laws that are constructed in response to some pre-existing situation. He we have Hobbes basing morality on observance of a social contract, which itself is a response to the unsatisfactory quality of life in the state of nature.
Consequentialist theories are also about actions. A good act is one which has some desirable consequences or other. It is a matter of debate as to what constitutes desirable consequences. They might be pleasure and avoidance of pain, happiness in some higher sense, quietude, etc. Further, they may hold for the individual or in general. Mill held that promotion of the general happiness is what makes a good act good.
The history of ethics has shown that it is difficult to maintain any of these theories in any pure or unmixed form. Is it enough that a person be virtuous or following a certain rule if the consequences of his actions are catastrophic? Can an action undertaken for the basest of motives, with accidentally favorable consequences, still be counted as good? Most ordinary people base their notions of morality on a combination of these factors. Mill tried to fit as much as possible into his consequentialist theory, but the attempt does not seem successful.
Anti-ethical theories have appeared throughout the history of philosophy and are held by many people. The skeptics held that no ethical theory could be justified (a point with which many people agree) and thus advocated a conventionalism: the right action is the one which conforms to prevailing custom.
A more sophisticated anti-ethical approach was undertaken by Nietzsche, who attempted to uncover an underlying basis for our ethical value judgments. They turn out to be consequences of deeper forces, primarily struggles for power. Thus approach, favored by many academics today, is called "deconstructionist." Nietzsche had in mind a replacement for ethics, something which lies "beyond good and evil," so perhaps his view is not entirely negative.
Another anti-moral stance is one of subjective relativism. The view here is that evaluative judgments express nothing but personal preferences, approval and disapproval. This approach was popular during much of the twentieth century, by philosophers who held that ethical judgments are not subject to scientific investigation. In that case, there are no ethical facts, only subjective responses to various forms of behavior.