The antonyms for the word "most conducting" are quite diverse. One of the simplest opposites of this term would be "least conducting." If a material is not good at conducting electricity or heat, it could be considered as having low conductivity. Similarly, the term "non-conducting" refers to materials that do not allow the flow of electrical or heat energy through them. Thus, materials like rubber, glass, and plastic can be considered non-conducting. Other antonyms for "most conducting" include insulating, obstructing, or blocking. These terms are often used in the context of electrical engineering, physics, and chemistry.