The way you remain both righteous and impartial is to never do anything consequential. That way, you can have the same effect for all parties while never doing anything you would find morally objectionable. It's essentially the trivial solution (magnitude of impact = 0), but is often implicitly advocated for in many debates here.
It occurred to me after writing this that there's a fourth variable: integrity, defined as your willingness to have principles and critically evaluate them against others' moral conduct. You could conceivably satisfy all of power, righteousness, and impartiality by assuming, in your value system, that everyone's values are morally acceptable and mutually compatible and hence there is no conflict between your values and everyone else's values. This is a position actually advocated by some philosophers, venture capitalists, and scientists! (There's a Tom Lehrer song in there somewhere: "Once zee rockets go up who cares where they come down / that's not my department / says Werner von Braun!") It's not a mainstream one within the general population, though; most people do actually have some feelings and pass some moral judgment on other people.
And yes, I was very deliberately trying to highlight the tension between objectivity and subjectivity here. (There's a lot of complexity over whether power is objective or subjective, too - power is your ability to enforce your will [subjective] over reality [objective], so it has elements of both.)