Onset adjectives are listed in this post. Each word below can often be found in front of the noun onset in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing ONSET.
abrupt, actual, acute, adolescent, adult, clinical, delayed, desperate, earlier
early, fast, faster, fierce, fiery, final, first, focal, fresh
furious, general, gradual, immediate, impetuous, initial, insidious, juvenile, last
late, later, new, peak, possible, quick, rapid, recent, second
slow, slower, spontaneous, subacute, subsequent, sudden, symptom, terrible, typical
unexpected, very, vigorous, violent
Hope this word list had the adjective used with onset you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.
Please add more adjectives to make this list more complete: