Regret adjectives are listed in this post. Each word below can often be found in front of the noun regret in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing REGRET.
affectionate, apparent, biggest, bitter, bitterest, certain, chief, considerable, constant, deep, deeper, deepest, equal, eternal, everlasting, evident, express, extreme
faint, fond, future, general, gentle, genuine, grand, great, greater, greatest, heartfelt, hopeless, inexpressible, infinite, intense, keen, keenest, last
lasting, later, least, less, lifelong, lingering, little, lively, long, melancholy, mere, mild, mingled, momentary, more, most, mournful, much
mutual, natural, obvious, old, only, other, own, painful, particular, passionate, personal, poignant, polite, profound, public, real, sad, same
secret, selfish, sensible, sentimental, serious, sharp, sincere, sincerest, single, slight, slightest, small, soft, sole, sorrowful, strong, subsequent, such
sweet, tender, true, unavailing, unfeigned, universal, unspeakable, useless, utmost, vague, vain, weak, wild, wistful
Hope this word list had the adjective used with regret you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.