Another way that the pigs betray the others is through their manipulation of the Seven Commandments. To see this in action, compare the Seven Commandment in chapter 2 with the single Commandment from chapter 10.
What you'll notice is that over time, the pigs manipulate the Commandments so that they enjoy a better standard of living than the others and, more importantly, so that their absolute power cannot be challenged.
In chapter 2, for example, the Commandments made every animal equal and forbade any behavior associated with humans, like wearing clothes or sleeping in a bed. But, as the novel progresses, the pigs want to live better than the other animals, so they change the Commandments accordingly. By the final chapter, there is only one Commandment and it strongly asserts the pigs' special status and dominance: "All animals are equal, but some animals are more equal than others."
This manipulation of the Seven Commandments is, therefore, a betrayal because it gives the pigs an elevated status and lots of privileges. They are no better off under the pigs than they were under Mr. Jones.