When it comes to finding synonyms for the phrase "authoritative command," there are many options available. One possibility is "dominant instruction," which conveys a similar sense of strength and control. Another option is "commanding directive," which emphasizes the idea of a clear and forceful order. "Imperative decree" is another phrase that can be used to describe an authoritative command, as it implies a sense of urgency and importance. Other possibilities include "decisive mandate," "firm ruling," and "unquestionable edict." Ultimately, the right choice will depend on the specific context in which the phrase is being used.