4 syllables:
capaciosly

3 syllables:
agency, blatancy, painfully, aimlessly, patiently, hastily, blazonry, faithfully, papacy, wastefully, specialty, gracefully, vagrancy, shamefully, maidenly, atony, blatantly, latency, fatally, faithlessly, masonry, blamelessly, racially, saliency, crazily, tastefully, gracelessly, vacancy, gratefully, shamelessly, actively, amity, candidly, cassidy, casuistry, clannishly, drastically, faddishly, flashily, gaspingly, gramineae, graphically, gravity, haptically, lavishly, magically, mattingly, naseby, panicky, pantingly, passively, radically, raffishly, ramblingly, raspingly, sanctity, savagely, slantingly, smashingly, stragglingly, tragically, validly, vanity

4 syllables:
favorably, press agency, outrageously, contagiously, freemasonry, courageously, mistakenly, disgracefully, news agency, naivety, belatedly, impatiently, complacency, insatiably, disdainfully, adactyly, attractively, banality, , bombastically, brutality, calamity, capacity, carnality, centrality, combatively, dramatically, ecstatically, emphatically, enchantingly, erratically, expansively, fantastically, fatality, grammatically, humanity, insanity, mechanically, mendacity, mentality, nostalgically, offhandedly, organically, outstandingly, plurality, protractedly, pugnacity, romantically, sarcastically, sporadically, syndactyly, tenacity, theatrically, venality, veracity

5 syllables:
unmistakably, unashamedly, inescapably, occasionally, travel agency, atonality, autocratically, automatically, brachytactyly, christianity, cordiality, criminality, cruciality, democratically, diplomatically, enigmatically, everlastingly, factuality, geographically, graduality, illegality, immorality, immortality, informality, inorganically, marginality, mutuality, nationality, personality, pertinacity, principality, punctuality, puritanically, rationality, single-handedly, sociality, speciality, symptomatically, systematically, technicality, unattractively, undramatically, ungrammatically, unromantically

6 syllables:
employment agency, mercantile agency, conceptuality, conditionality, conventionality, diagrammatically, directionality, effectuality, emotionality, enthusiastically, eventuality, impartiality, instrumentality, intentionality, materiality, originality, orthogonality, proportionality, sentimentality, split personality, traditionality, undemocratically, undiplomatically, unsystematically

7 syllables:
cyclopean masonry, rotational latency, advertising agency, anal personality, constitutionality, counterfactuality, cult of personality, immateriality, individuality, ineffectuality, internationality, oral personality, superficiality, unconventionality, unemotionality, unenthusiastically, unoriginality

8 syllables:
regulatory agency, genital personality, heterosexuality, multiple personality, sexual immorality

9 syllables:
central intelligence agency, psychopathic personality

11 syllables:
environmental protection agency

14 syllables:
international atomic energy agency