2 Syllables: SU
biggest, bigots, billets, biscuits, bishops, bismuth, bridges, busiest, business, Christmas, citrus, dearest, digits, dishes, fishes, fittest, frigates, Griffith, grimace, hillocks, isthmus, kisses, limits, listless, minutes, minutest, mischief, mistress, nearest, Nicholas, nitrous, Philips, pickets, quibus, riches, richest, richness, ridges, rivets, spinach, stiffness, swiftest, swiftness, switches, thickets, tickets, vicious, visage, viscous, vistas, witches
3 Syllables: USU
ambitious, archbishops, assiduous, auspicious, bacillus, capricious, delicious, elicits, exhibits, factitious, fictitious, forgiveness, inhibits, judicious, lascivious, malicious, Narcissus, nutritious, oblivious, officious, pernicious, prestigious, prodigious, prohibits, propitious, religious, seditious, severest, sincerest, suspicious, utilise
4 Syllables: UUSU
adventitious, avaricious, Dionysius, expeditious, injudicious, irreligious, superstitious, surreptitious, unpropitious, unsuspicious
Found 92 words across 3 groupings. Skipped 4 excess words of a similar stem.