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

anthropomorphization compartmentalisation compartmentalization counterdemonstration duoquinquagintillion electrogalvanization endophotocoagulation hydrodesulfurization institutionalisation institutionalization internationalisation internationalization microminiaturization nonillionsedecillion photophosphorylation piezocrystallization pseudosophistication quattuorvigintillion quinquatrigintillion sesquinquagintillion