"Most onrushing" refers to the act of advancing or approaching rapidly or aggressively. Its antonyms would be words that imply a slower, more gradual, or less forceful movement. Such antonyms could include: delayed, hesitant, calm, cautious, gentle, slow, steady, relaxed, unhurried, and leisurely. These are words that communicate a sense of measured progression, taking one's time, and proceeding with care and deliberation. They are the antithesis of the adrenaline-fueled rush that characterizes "most onrushing." By using these words, we can convey a mood that is much more tranquil, contemplative, and patient - the perfect counterweight to the frenzied urgency of "most onrushing.