immense

astronomical (also astronomic), Brobdingnagian, bumper, colossal, cosmic (also cosmical), cyclopean, elephantine, enormous, galactic, gargantuan, giant, gigantesque, gigantic, grand, herculean, heroic (also heroical), Himalayan, huge, humongous (also humungous), jumbo, king-size (or king-sized), leviathan, mammoth, massive, mega, mighty, monster, monstrous, monumental, mountainous, oceanic, pharaonic, planetary, prodigious, super, super-duper, supersize, supersized, titanic, tremendous, vast, vasty, walloping, whacking, whopping

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], jim-dandy, keen, lovely, marvelous (or marvellous), mean, neat, nifty, noble, number one (also No. 1), 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