number one

arch, big, capital, cardinal, central, chief, dominant, first, foremost, grand, great, greatest, highest, key, leading, main, master, numero uno, overbearing, overmastering, overriding, paramount, predominant, preeminent, premier, primal, primary, principal, prior, sovereign (also sovran), supreme

A-OK, A1, awesome, bang-up, banner, beautiful, blue-chip, blue-ribbon, boffo, bonny (also bonnie) [chiefly British], boss [slang], brag, brave, bully, bumper, capital, choice, classic, cool [slang], corking, crackerjack, cracking, dandy, divine, dope [slang], down [slang], dynamite, excellent, fab, fabulous, famous, fantabulous [slang], fantastic, fine, first-class, first-rate, first-string, five-star, four-star, frontline, gangbusters (also gangbuster), gilt-edged (or gilt-edge), gone [slang], grand, great, groovy, heavenly, high-class, hot, hype [slang], immense, jim-dandy, keen, lovely, marvelous (or marvellous), mean, neat, nifty, noble, numero uno, out-of-sight [slang], par excellence, peachy, peachy keen, phat [slang], prime, primo [slang], prize, prizewinning, quality, radical [slang], righteous [slang], sensational, slick, splendid, stellar, sterling, superb, superior, superlative, supernal, swell, terrific, tip-top, top, top-notch, top-of-the-line, top-shelf, topflight, topping [chiefly British], unsurpassed, wizard [chiefly British], wonderful