Adjectives ending with the letter S are listed in this post.
acrimonious, advantageous, adventurous, after-hours, agricultural-products, aimless, all-news, ambiguous, ambitious, amiss, analogous, anomalous, anonymous, anti-virus, anxious, a-plus, arduous, artless, atrocious, audacious, auspicious, autonomous, auto-parts
barbarous, bare-bones, baseless, behind-the-scenes, billion-plus, bogus, boisterous, bourgeois
calamitous, callous, cancerous, capricious, careless, cashless, cautious, cavernous, childless, colorless, conscientious, conscious, conspicuous, contagious, contemptuous, contentious, contiguous, continuous, copious, cost-conscious, countless, courageous, crass, cross, curious
dangerous, defenseless, deleterious, delicious, diaphanous, disadvantageous, disastrous, disingenuous, dubious
effortless, egregious, eighties, endless, enormous, erroneous, euphonious, excess, express, extraneous
fabulous, facetious, fallacious, famous, fashion-conscious, fastidious, faultless, fearless, featureless, ferocious, fictitious, firecrackers, first-class, first-timers, flawless, flirtatious, fractious, frivolous, fruitless, furious
gaseous, generous, glamorous, glorious, gorgeous, gracious, grass-roots, gratuitous, gregarious, grievous, gross, groundless
hapless, harmless, harmonious, hazardous, health-conscious, heartless, heinous, helpless, hers, hicks, hideous, high-class, high-stakes, hilarious, homeless, homogeneous, homogenous, hopeless, horrendous, human-rights, humorless, humorous
illustrious, impecunious, imperious, impervious, impetuous, inauspicious, incongruous, indigenous, infamous, infectious, ingenious, innocuous, insidious, instantaneous, intravenous
jealous, jobless, jones, joyless, joyous, judicious
languorous, lawless, lecherous, less, lifeless, limitless, listless, litigious, loquacious, lower-middle-class, low-stress, ludicrous, luminous, luscious, luxurious
malicious, marvelous, mass, meaningless, mellifluous, melodious, meticulous, middle-class, million-plus, mindless, miraculous, miscellaneous, mischievous, momentous, monstrous, motionless, murderous, mutinous, mysterious
nameless, natural-gas, nauseous, needless, nervous, nichols, no-frills, no-illusions, non-religious, notorious, noxious, numerous, nutritious, nuts-and-bolts
oblivious, obnoxious, obvious, odious, off-limits, ominous, omnibus, on-campus, onerous, ours, outrageous, overseas, overzealous
painless, peerless, perfidious, perilous, pernicious, pilgrims, pious, plainclothes, pointless, poisonous, ponderous, populous, porous, portentous, powerless, precarious, precious, precipitous, precocious, preposterous, prestigious, presumptuous, pretentious, previous, price-earnings, priceless, pro-business, prodigious, promiscuous, propitious, prosperous, public-relations, public-works, pugnacious
rambunctious, raucous, rebellious, reckless, relentless, religious, remiss, repetitious, restless, ridiculous, righteous, rigorous, ruinous, ruthless
salacious, sales, scandalous, self-conscious, self-righteous, senseless, sensuous, serious, seven-eighths, shirtless, simultaneous, sinus, slow-news, small-arms, smokeless, social-services, solicitous, soothsayers, soup-to-nuts, spacious, spontaneous, spotless, spurious, stainless, stateless, strenuous, studious, sumptuous, superfluous, surplus, suspicious, swiss, synchronous, synonymous
tasteless, tedious, tempestuous, tenacious, tendentious, tenuous, thankless, theirs, think-tanks, third-class, thoughtless, timeless, tireless, toothless, topless, tortuous, treacherous, tremendous, tremulous, trimmers, tumultuous
ubiquitous, unambiguous, unanimous, unconscious, unglamorous, unpretentious, unscrupulous, unserious, upper-class, urbanites, useless
various, vicious, victorious, vigorous, vociferous, voluminous, voluptuous, voracious
windowless, wireless, wondrous, working-class, world-class, world-famous, worthless
zealous
Hope this word list had the adjective that ends in S you were looking for. Additional descriptive words can be found in the other pages on this site.
Stupendous