Or search: toxic, malign, subtle, nocent, abusive, hurtful, noxious, ruinous, bruising, damaging, injurious, insidious, offensive, libellous, defamatory
1 Syllable: S
Charles
2 Syllables: SU
Arnold, Arnold's, artful, Carmel, carnal, garbled, marble, Marshal, Marshall, Marshall's, marshals, martial, marvel, parcel, partial, snarled, sparkle, startle
3 Syllables: USU
impartial
4 Syllables: UUSU
patriarchal

Found 21 words across 4 groupings. Skipped 8 excess words of a similar stem.