How does Orwell warn us about the abuse of power in Nineteen Eighty -Four?
The entire book is a warning about the abuse of power. The inner party controls almost all aspect of everyone's life. They do this in many ways. The "Thought Police" are always there, to catch you if you do or say anything against the existing powers. They control reality by providing you with whatever information they want you to have. If they promise you'll have 25 grams of chocolate this year and they can't deliver, they just destroy any references to the earlier prediction, rewrite it and predict 15 grams, and then announce 20 grams which is a big improvement over what they "had predicted." They do this with people who disappear, people whose loyalties are "compromised" --- anything to support what they need you to believe. (This is also one way that reality as we know it is destroyed.)
The creation of false enemies is another way the state abuses its power to keep you under control. There is always someone to be afraid of, someone you need protection from, some crisis that needs to be dealth with. In some ways this is reminiscent of some of the arguments about giving up freedom for safety after 911 and also part of the discussion of what is happening today as we are told over and over again how bad things are and how many crises we face with the aim of our giving over more and more power to the administration that will save us.
And the greatest abuse of power --- they use it not for any purpose, not as a tool, but for its own sake. They use it so effectively that they actually wipe out "reality" when they get Winston to admit and BELIEVE that 2 + 2 = 5. We see the ultimate abuse of power when the state has this much ability to create/control "reality" (if we can call it that because it no longer really exists).