Or search: madly, toxic, lethal, mortal, noxious, baneful, divinity, theology, venomous, virulent, deucedly, insanely, intensive, pestilent, devilishly
2 Syllables: SU
breakfast, chariot, dexterous, eldest, Eliot, Eliot's, Elliot, Elliott, extras, Harriet, headless, heaviest, helmet, helpless, lettuce, necklace, nexus, pelvis, plexus, readiest, reckless, redness, selfless, sexes, Texas, various, velvet, wealthiest, wreckage
3 Syllables: SUU
penniless, readiness
3 Syllables: USU
calcareous, correctness, directness, gregarious, hilarious, infectious, nefarious, precarious, prospectus, rebellious, vicarious
4 Syllables: UUSU
commissariat, multifarious, proletariat, Secretariat

Found 46 words across 4 groupings. Skipped 3 excess words of a similar stem.