Upon reading the topic of your composition it is inevitable to quote Blaise Pasca:
Justice and power must be brought together, so that whatever is just may be powerful, and whatever is powerful may be just.
Your composition may very well start with this quotation, followed by your introductory paragraph, in which you will also include your main subtopics, followed by a closing statement.
Indent to cite QUOTE
Blaise Pascal (1623-1662)
Your introductory statement should state that the creation of power through justice entails that the rights, safety, and privileges of all individuals will be uncorrupted and protected. The balance that exists in a fair and functional society will remain working productively by watching out for the equal benefit of all members of society.
From your introduction you can continue to elaborate on what that means and what it entails. It also piggy-backs on the Pascal quote, which you can further touch upon at the closing of your essay, or of your main statement if that is the case.
A supporting fact for this mains statement could state that, when power is obtained through justice, the power will often be well-managed. All sectors will benefit from seeing the fairness of the process with which the power is gained and, as a result, the trust of the people in the powers that be will remain untouched.
You mentioned that you could not mention the word injustice, but if you are allowed to compare and contrast your could add that when power is obtained through injustice, only one sector benefits by disenfranchising and abusing the rights of those who are not in the dominant group. As a result, the lack of checks and balances commences to create the distrust and resentment that leads to social fragmentation.
Then as your closing statement you may revisit the quote by Pascal and explain it a little further as it applies to your main statement. An example could be:
Therefore, like Blaise Pascal argues "whatever is just is powerful, and whatever is powerful is just". Power and its origin become a powerful combination which can either make or break a group through stability or instability.
Use these ideas and synthesize and use your own voice so that you can express with more creativity that, once power is obtained through justice the system of checks and balances of society will remain in place, hence ensuring and safekeeping the rights and privileges of the people.