The phrase "opposing side" refers to a different group or people who hold a different opinion, belief, or position on a particular matter or issue. It represents the people or arguments that are against your own viewpoint or stance. Full definition
Each team has a base on opposing sides of the street. (thekoalition.com)
When in a car or a building, open windows as often as possible, preferably on opposing sides of the space for cross ventilation. (articles.mercola.com)
From opposing sides, two heroes are set on a collision course that will decide the fate of their family, their people and their home. (thehollywoodnews.com)