The word "departing" means leaving or going away. Its antonyms could include staying, remaining, arriving, entering, or returning. When someone is departing from a place, the opposite would be arriving at the same location. When someone is departing from a job, the opposite would be staying in that position or even returning to it. Departing can also mean passing away, and in that sense, the opposite would be being born or coming into existence. Different situations call for different antonyms of departing, but they all share a sense of staying or arriving instead of leaving.