The opposite of "were one side" could be "were on opposite sides." This implies a division, conflict or difference in opinions or beliefs between two or more parties. Other antonyms for "were one side" could include "united," "aligned," "cohesive," or "together." These words suggest a sense of harmony, agreement, and cohesion among individuals or groups. When people are "on the same page," they share a common understanding and work towards a common goal. On the other hand, when people are on opposite sides, they are divided and may have conflicting views, leading to tension and disagreement.