Opponent adjectives are listed in this post. Each word below can often be found in front of the noun opponent in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing OPPONENT.
able, active, aggressive, american, ardent, armed, avowed, bitter, bitterest, chief, consistent, constant, convinced, dangerous, declared, democratic, determined, distinguished
early, earnest, effective, fair, fallen, famous, fanatical, fierce, firm, first, foremost, former, formidable, future, good, great, greatest, honorable
honourable, human, illustrious, imaginary, implacable, inveterate, invisible, last, late, leading, learned, lifelong, longtime, main, major, new, next, obstinate
old, only, open, other, outspoken, own, particular, passionate, persistent, personal, political, possible, potential, powerful, primary, principal, prominent, real
republican, resolute, same, second, serious, single, staunch, strenuous, strong, stronger, strongest, sturdy, successful, superior, time, tough, toughest, troublesome
uncompromising, unscrupulous, vanquished, vehement, victorious, vigorous, violent, vocal, vociferous, weak, weaker, whig, worthy, young, zealous
Hope this word list had the adjective used with opponent you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.