There are many words that can be used as synonyms for the phrase "makes inactive". For example, "deactivate" is a common synonym that emphasizes the removal of activity or energy from something. "Disable" is another synonym that refers to the cessation of function or activity. Other synonyms include "quell", "suppress", and "stifle", all of which represent the act of putting an end to or preventing activity. "Extinguish" is a strong synonym that implies complete and permanent inactivity. Ultimately, the choice of synonym will depend on the context in which it is being used and the specific connotations that are desired.