The two paramount principles of Nietzschean philosophy are the concepts of the Last Man and the Ubermensch. These two concepts are the human-form archetypes of two fundamentally opposing concepts of the meaning of life, the former being that life's purpose is to indulge in pleasures, with no regard to quality, while at the same time eliminating pain. This path leads to degeneracy, and the Last Man is an individual or a collective that partakes in this path of decay and feels perfectly comfortable in doing so, to the point where any opposition to this feeling on the part of another individual makes that individual fit for "the madhouse" (TSZ prelude section 5) .
The Ubermensch sees value in life in the exact opposite, meaning he acts with disregard to "happiness," in the sense of the Last Man's artificial construct of the term, and leads a life of creation and ascension. This type does not seek out any sort of 'perfection' nor a specific 'virtue,' but does act in direct contrast to the degenerating actions of the Last Men by not partaking in a degenerate lifestyle and thereby seeking out 'quality' pleasures.
Although the Ubermensch and Last Man have opposite views on the meaning of life, they are not, thereby, opposite men. The opposite of the Ubermensch or 'Overman' would have to be rendered in the word Untermensch or 'Underman', a term which never is written in Nietzsche's philosophy, but can be rendered with different terms he uses, such as Chandala. This Untermensch is a type who is physiologically unable to take on "Overmanly" characteristics. Because of his physical disadvantage to the type "man," he must do what he can to drag down man, whether is a conscious actor in this process or not.
The Untermensch may make use of a Slave Morality in order to infect humanity and thereby discourage the formulation of an Ubermensch, which, to them, is a devil. This Slave Morality posits that overmanly characteristics are "Evil," while the characteristics of the Untermensch are all "Good." This Slave Morality was created to counter the Overmanly "Master Morality," or the belief that the "Good" are comprised of the beautiful, intelligent, and physically able, while the "Bad" are comprised of the ugly, stupid, and physically handicapped. A "Master Moralist" believes the maintenance of the "Good" is of the utmost importance, even if it comes at the expense of the "Bad."
The Last Man, thereby, is the type "man" who has been infected by the slave morality of the Untermensch. Christianity has been the most successful morality for creating the type Last Man to date, but in recent times has lost influenced and has been replaced by even more subversive ideologies in some places. The highest formulation of the archetype Ubermensch is the man who pulls mankind out of its collective Last-Man-like tendencies and inspires a Renaissance of Overmanly individuals, thereby creating a new mankind.