Or search: exempt, immune, absolve, excused, forgive, relieve, untaxed, dispense, unratable, deregulate, nontaxable, privileged, derestrict
2 Syllables: SU
bended, Bennet, Bennett, blended, ended, friendship, mended, rented, scented, Senate, splendid, tempted, tended, vented
3 Syllables: SUU
segmented
3 Syllables: USU
amended, appended, Appendix, assented, authentic, befriended, cemented, commended, concentric, consented, contended, contented, defended, demented, depended, descended, dissented, distended, eccentric, endemic, expended, extended, forensic, Hellenic, indented, intended, invented, lamented, offended, polemic, pretended, prevented, relented, repented, suspended, systemic, transcended
4 Syllables: UUSU
academic, circumvented, comprehended, condescended, discontented, epidemic, hygienic, pathogenic, recommended, represented, supplemented, unattended, undefended, unfrequented, unintended
5 Syllables: UUUSU
misrepresented, superintended

Found 69 words across 5 groupings. Skipped 4 excess words of a similar stem.