The phrase "going too far" is often used to express the idea of crossing a line or exceeding appropriate boundaries. There are several synonyms that can be used to convey this concept. For example, "overstepping" implies that someone has gone beyond what is considered acceptable or appropriate. "Pushing the envelope" suggests that someone is testing the limits of what is possible or allowed. "Going overboard" implies that someone has gone to an extreme, often with negative consequences. "Crossing the line" is a direct way of expressing that someone has gone too far, often in a way that is unacceptable. Ultimately, these synonyms all convey the idea of excessive behavior that results in negative outcomes.