In the final chapter of the novella, Benjamin and Clover enter the barn and discover that the Seven Commandments have been painted over. The commandments have been replaced with one that simply reads: "ALL ANIMALS ARE EQUAL BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS." This contradicting statement underscores the inequality between the pigs and the other animals on the farm, which has existed since Mr. Jones's expulsion.

Although Animal Farm was founded on solidarity, equality, and the principles of Animalism, the pigs have enjoyed special privileges from the beginning. Shortly after old Major passes away, the pigs take a leading role in developing the principles of Animalism, educating the animals, and preparing them to rebel.

Following the Rebellion, the pigs become leaders of the farm and exercise their authority by establishing policies and managing the other animals. Napoleon, Snowball, Squealer, and the other pigs enjoy apples and milk in their mash and exempt themselves from arduous labor. They also label themselves "brainworkers" and spend the majority of their day organizing the farm. Shortly after Napoleon usurps power, the pigs segregate themselves from the other animals by living in the farmhouse, sleeping in beds, educating themselves, drinking alcohol, and exploiting the other animals' labor.

The final commandment reaffirms the privileged status of all pigs, which has existed since the inception of Animal Farm. The pigs have always enjoyed special privileges and controlled the other animals using various propaganda techniques since the beginning.

After Snowball is banished from the farm, all the seven rules are edited. This change is first identified by Clover who asks Benjamin to confirm it. The single rule on the wall runs, "ALL ANIMALS ARE EQUAL BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS." This significant evolution of the seven commandments allows the pigs extra privileges and justifies all their questionable decisions.

From the beginning of the text, it is clear that “some animals are more equal than others.” And by the end of the novel, the pigs are sleeping in beds, consuming alcohol, eating apples, and trading with humans, which is contrary to the initial principles of Animalism. Unlike other animals, the pigs now walk on their hind legs and dress like humans.

Napoleon and his fellow pigs practice a behavior they once despised. In the end, the difference between the pigs and humans is not quite clear. As Orwell puts it, “The creatures outside looked from pig to man, and from man to pig, and from pig to man again: but already it was impossible to say which was which."

The new Commandment is that "ALL ANIMALS ARE EQUAL BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS." This has been true from the beginning of Animal Farm because Snowball, Napoleon, and the other pigs have always held privileged positions on the farm. They can read and write better than any of the other animals on the farm, many of whom can't read at all. At first, Snowball and Napoleon also control all the proposals put forward during the debates on the farm, and none of the other animals make proposals.

The pigs also claim the cozy harness room for themselves, and they receive the best food on the farm--milk for their mash and windfall apples. Squealer, also a pig, explains to the other animals that the pigs deserve the best food because "We pigs are brainworkers. The whole management and organization of this farm depend on us." The pigs constantly maintain that they deserve better than the other animals, and they scare the other animals into agreeing with them because they claim that if they weren't in control, Jones would come back to the farm. However, the other animals do most of the hard work on the farm, while the pigs claim the best position and perks for themselves. This commandment has therefore been true since the beginning of the animals' takeover of the farm.

By the end of George Orwell's novel, Animal Farm, the final revision of the commandments reads "ALL ANIMALS ARE EQUAL BUT SOME ANIMALS ARE MORE EQUAL THAN OHERS." The pigs have always considered themselves "more equal" than the other animals: They took control from the start, allowed themselves more food, less work and better living conditions. They eventually moved into the house, slept in the beds, drank liquor and began wearing clothing. They considered themselves more intelligent and proved that it was true by continuously convincing the others that it was all for the betterment of the farm. Finally, the pigs became indistinguishable from the humans with whom they did business.

At the end of the book, in Chapter 10, there is only one commandment left.  It is

ALL ANIMALS ARE EQUAL
BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS

This has always been true because the pigs and, to some extent, the dogs, have always been "more equal" than the other animals.

Throughout the story, the pigs have enjoyed more privileges than anyone else.  All the leaders have been pigs.  The pigs, for example, have been the ones who got to have all the milk whereas it used to be given to the hens.  In addition, the pigs get all the apples.

Things like that show that the pigs have always gotten more than their fair share.

By the end of Animal Farm, in chapter 10, the original Seven Commandments have been reduced to one, and this one has been changed from its original statement, "all animals are equal," to read "all animals are equal, but some animals are more equal than others."

Of course, it is logically impossible for some animals to be "more equal than others." Nevertheless, this has been the case, if not from the beginning of the animals taking over the farm, then from very soon after. Almost from the start, the pigs set themselves apart as the leaders and brainworkers and use this to justify extra privileges, such as eating the windfall apples themselves. This sense of privilege gradually gets worse and worse, especially after Snowball is run off the farm and Napoleon takes over, until, finally, the pigs live entirely separately and differently from the other animals. In fact, they live as human beings.

In the beginning of life under rule of the animals of Animal Farm, there were seven commandments. Perhaps the most important was the seventh--"All animals are equal." Though many of the animals never realized it, this commandment was broken almost immediately by the pigs. Beginning with the theft of the milk for their own consumption, the pigs used the other animals much in the same way Mr. Jones had. By Chapter 10, Napoleon was walking on two legs and dining with humans. When Clover and old Benjamin took a look at the end of the big barn, there was only one commandment remaining:

                      ALL ANIMALS ARE EQUAL
  BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS

Some of the Animal Farm animals seemed to remember that changes had been made to the original commandments, but the pigs assured their comrades that nothing had really been altered. Originally there were seven commandments, but eventually every single one was amended by the pigs. The most important was the seventh: "All animals are equal." In the end, there remained only one commandment, and it, too, had been changed. It now read "ALL ANIMALS ARE EQUAL BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS." This commandment had always been true, since from the start, the pigs had abused their rule of equality, always maintaining an upper hand over the others.

I assume that you are talking about the one commandment that is left by the time the pigs get through with things.  This is seen towards the end of Chapter 10.  The commandment says that "All animals are equal, but some animals are more equal than others."

This has been true ever since the beginning because the pigs (and to some extent their enforcers, the dogs) have been more equal ever since the beginning.  Even at the very beginning, only the pigs have ever had leadership positions.  At Old Major's speech, it is all pigs in the front row.  Soon after the revolution, we find that the pigs are not really doing any manual labor and they are having the easiest lives -- like getting the milk the hens used to share.

So the pigs have been on top from the start.