Antonyms for the phrase "at leading edge" are numerous and include terms like behind the times, conventional, outdated, old-fashioned, passe, traditional, and retrograde. While "at leading edge" is commonly used to describe something or someone that is innovative, modern, and forward-thinking, these antonyms suggest the opposite: a lack of progress, stagnation, and resistance to change. They indicate a position in the past or a reluctance to embrace new ideas and technologies. While some may view being at the leading edge as risky or unstable, being behind the times can be equally detrimental in a rapidly evolving world.