The antonyms for "acted as middle" could be "ignored," "sidestepped," or "avoided." These words suggest a refusal to take responsibility and engage in a situation. Instead of stepping up and mediating, someone who ignores or sidesteps an issue may be seen as passive or cowardly. Conversely, someone who avoids acting as a middleman may do so to avoid creating conflict or exacerbating an already-polarized situation. Antonyms for "acted as middle" indicate a sense of neutrality or distance, and suggest a reluctance to become involved in the process of negotiation or decision-making.