The phrase "beating down upon" is a common expression that describes the intense and sustained impact of something upon an object or person, typically associated with the sun's rays or heavy rain. Some antonyms for this phrase could include soft, gentle, mild, moderate, or soothing. These words suggest a less forceful, less aggressive impact or experience, such as a light breeze, a calm stream, a gentle touch, or a pleasant temperature. Using these antonyms can help to convey a different mood or tone in writing, such as creating a sense of calm or comfort rather than intensity or discomfort.