Mammoth Uncensored Word List:
19 words ending with us, 16 letters long

anthropomorphous hypersynchronous hypocotyledonous lymphangiomatous monocotyledonous musculocutaneous noncarboniferous noncarcinomatous nonexanthematous nonfossiliferous noninstantaneous nonmetalliferous nonsanctimonious organophosphorus overpresumptuous palatopharyngeus pseudomembranous sclerenchymatous supersynchronous