2 syllables:
justice

3 syllables:
do justice, chief justice, augustus, bottomless, cognizance, columnists, commonness, communists, confidence, conscienceless, consciousness, consequence, consonance, continence, continents, documents, dominance, godlessness, honestness, modestness, monuments, noxiousness, obstinance, occupants, oculus, ominous, omnibus, omphalus, onymous, opulence, oxalis, pompousness, populace, populous, populus, profitless, prominence, prophetess, protestants, provenance, providence, romulus, rottenness, scolytus, slothfulness, somnolence, spotlessness, squalidness, stolidness, strophanthus, vomitus, watchfulness

4 syllables:
abdominous, acrogenous, acromphalus, acropolis, ammotragus, androgenous, anonymous, anthophagous, apogamous, apophasis, astomatous, autogenous, autologous, autolysis, autonomous, carpophagous, cryptogamous, cytolysis, endogamous, eponymous, esophagus, exogamous, gymnopilus, hippotragus, homologous, hydrolysis, hypothesis, idolatress, improvidence, incompetence, incontinence, lose consciousness, melophagus, metropolis, monogamous, monotonous, necropolis, nitrogenous, obnoxiousness, oesophagus, panonychus, pathologists, phytophagous, predominance, psychologists, recognizance, reconnaissance, saprophagous, sarcolemnous, sarcophagus, self-confidence, self-consciousness, subconsciousness, synonymous, taurotragus, uncommonness, uropsilus, with confidence, zoophagous

5 syllables:
poetic justice, acantholysis, air reconnaissance, amylolysis, anisogamous, anthropophagus, campylotropous, creeping oxalis, disconsolateness, electrolysis, entomophilous, fibrinolysis, genus oxalis, haematolysis, hematolysis, heterologous, hippopotamus, loss of consciousness, megalopolis, nonautonomous, nonnitrogenous, ophiophagus, proteolysis, semiconsciousness, stephanopoulos, stream of consciousness, unselfconsciousness, vote of confidence

6 syllables:
department of justice, adrianopolis, bacteriolysis, bacteriophagous, megalobatrachus

7 syllables:
displaying incompetence, genus hippopotamus

8 syllables:
alcoholics anonymous, electronic reconnaissance, urinary incontinence

9 syllables:
international court of justice

15 syllables:
international society for krishna consciousness