The phrase "renders inert" means to deactivate or make something inactive. Its antonym, therefore, would be something that activates or energizes. Some possible antonyms include "activates," "enlivens," "stimulates," "invigorates," "revitalizes," "awakens," "juices up," "rejuvenates," "vitalizes," "stirs up," or "ignites." These words suggest actions that bring energy, life, and movement back to something that was once stagnant or immobile. They are useful concepts in the context of physical, mental, or emotional revitalization, whether for a person, an object or a system that has lost its power and needs to be awakened.