Or search: mild, clement, equable, restrained, abstemious
2 Syllables: SU
Bennett, dentist, ended, Lennox, Lenox, rented, Senate, tempest, template, tempted, tended, tenet
3 Syllables: SUU
gentlest
3 Syllables: USU
apprenticed, ascended, attempted, attended, augmented, contented, defended, depended, descended, extended, fermented, invented, offended, presented, pretended, relented, resented, suspended
4 Syllables: USUU
commensurate, degenerate, intemperate
4 Syllables: UUSU
apprehended, recommended, represented

Found 37 words across 5 groupings. Skipped 2 excess words of a similar stem.