"Passed the Rubicon" is a phrase that refers to a critical turning point or a moment of no return. It is derived from the crossing of the Rubicon river by Julius Caesar and his army in 49 BC, which marked the start of a civil war. To convey a similar sentiment, one could use multiple synonyms such as "point of no return," "reached the threshold," "crossed the line," "gone too far," "irrevocable decision," or "set on a course." These phrases suggest a significant decision or action that cannot be undone or reversed. In other words, once the Rubicon is crossed, there is no going back.