Mammoth Uncensored Word List:
34 words ending with ns, 20 letters long

adrenocorticotropins antiparliamentarians autotransplantations conventionalizations countermobilizations cytodifferentiations dehydrochlorinations deindustrializations departmentalizations homotransplantations immunoprecipitations intellectualizations interstratifications microstratifications mischaracterizations nonagintacentillions octogintacentillions overdifferentiations overprocrastinations phacoemulsifications photodisintegrations photointerpretations professionalizations quinquavigintillions reconceptualizations reindustrializations septentrigintillions sexagintacentillions superspecializations ultracentrifugations underrepresentations unquinquagintillions unviginticentillions xenotransplantations