The antonyms for the word "most killing" are words that imply less devastating or harmful. These words include "nonfatal," "mild," "harmless," and "gentle". "Nonfatal" indicates that an action or event did not lead to death, while "mild" implies that something was not severe or intense. "Harmless" means that something was not dangerous or harsh, while "gentle" suggests that an action was done in a kind or sensitive way. Choosing the appropriate antonym for "most killing" depends on the context and the level of severity intended.