(most valuable) adjective
best, beyond all praise, beyond compare, capital, cardinal, champion, chief, choice, crowning, dominant, eminent, excelling, exceptional, exemplary, exquisite, finest, first-class, first in quality, first-rate, foremost, front, greatest, head, highest, important, leading, matchless, nonpareil, of highest excellence, of the best quality, optimas, paramount, peerless, predominant, preeminent, preponderant, prevailing, priceless, principal, prize, prominent, remarkable, select, specially selected, splendid, superb, supereminent, superior, superlative, supreme, top, transcendant, unequaled, unmatched, unparalleled, unrivaled, unsurpassable, unsurpassed, utmost, without comparison
aboriginal, authentic, basal, basic, beginning, dawning, earliest, early, elemental, elementary, embryonic, first, formative, fossil, fundamental, generative, genuine, germinal, inaugural, inceptive, incipient, initial, institutive, introductory, native, oldest, originative, primal, primary, primeval, primitive, primordial, primus, rudimentary, starting
cardinal (basic), cardinal (outstanding), dominant, edify, educate, important (significant), initiate, instruct (teach), leading (ranking first), major, master, meritorious, necessary (required), notable, original (initial), paramount, premium, primary, primordial, principal, professional (stellar), ripe, salient, select, sterling, superlative
Burton's Legal Thesaurus. William C. Burton. 2006
adj.First; most important.
The Essential Law Dictionary. — Sphinx Publishing, An imprint of Sourcebooks, Inc. Amy Hackney Blackwell. 2008.