Onsetting refers to the beginning or start of something. Antonyms for onsetting include cessation, discontinuance, and termination, which all indicate an end or conclusion. Another antonym is conclusion, which refers to the end of something that has been ongoing. Opposite to onset, there are words such as decline or wane, which imply a decrease or reduction in intensity or frequency rather than the beginning of something. Other antonyms for onsetting include end, finale, and culmination, which all imply that something is concluding, coming to an end, or reaching its peak. Overall, antonyms for onsetting involve the end or conclusion of an event, rather than the initial starting point.