There a myriad of possible ONE's, but a few are more common and powerful than others…

The United Empire

Imperium Sanctus <The Holy Empire>

天下大中國 (Tian Xia Da Zhong Guo) <Under Heaven Great Central State>

The Aryan Reich

The Alexandrian Empire

The One Nation Empire is not a specific individual empire, but rather a typical legacy of human civilization. In many of the parallel worlds, single groups of people eventually succeed in taking over the world and dominating it. These are referred to collectively as the One Nation Empires or One Nation Earths. In general each ONE does not particularly get along with any other ONE, but often find common cause against the Allied Worlds.

There a myriad of possible ON Es?, but a few are more common and powerful than others…

The United Empire If the American Revolution had failed, and the British Empire had remained the dominant world power for far longer, this is what we get.

Imperium Sanctus <The Holy Empire> A result of what would happen if the Roman Empire had never collapsed and there was never a Protestant Reformation to weaken the Catholic Church.

天下大中國 (Tian Xia Da Zhong Guo) <Under Heaven Great Central State> Basically this is what would happen if China were more aggressive and united throughout history.

The Aryan Reich Basically if the Nazis had won World War II, we get this.

The Alexandrian Empire This is what would have happened if Alexander the Great had lived longer.