Or search: unhelpful
2 Syllables: SU
druggist, luggage, publish, rubbish, sluggish, uplift
3 Syllables: USU
constructive, destructive, disruptive, inductive, instructive, obstructive, productive, republished, seductive, unpublished
4 Syllables: UUSU
reproductive, unproductive

Found 18 words across 3 groupings. Skipped 1 excess word of a similar stem.