Antonyms for the phrase "tickle to death" could include terms such as "seriousness," "solemnity," and "dullness." These words may be used to describe a lack of lightheartedness or humor in a situation. Additionally, other antonyms may include words such as "saddening," "depressing," or "disheartening," which can describe the opposite of the joy and laughter associated with tickling. Overall, the antonyms for tickle to death are words that express sadness, gravity, and a lack of humor or lightness.