Or search: dire, awful, dread, dreaded, fearful, alarming, dreadful, horrific, horrendous, frightening
2 Syllables: SU
clearance, Cyprian, Ephraim, ference, Miriam, miscreant, Pearson, serum, Syrian, theorem
3 Syllables: USU
adherence, adherent, appearance, Assyrian, coherence, coherent, criterion, delirium, experience, imperium, Macpherson, reappearance, Shakespearean, Siberian
4 Syllables: UUSU
disappearance, equilibrium, Hanoverian, incoherence, incoherent, inexperience, interference, perseverance, Presbyterian

Found 33 words across 3 groupings. Skipped 8 excess words of a similar stem.