Mammoth Uncensored Word List:
27 words ending with f, 11 letters long

bulletproof bullmastiff counterbuff creaseproof daggerproof ecologistsf greaseproof infangthief insectproof leatherleaf mantelshelf mildewproof neckerchief needleproof pilferproof ploughstaff poisonproof showerproof shrinkproof sliverproof splashproof strifeproof tamperproof terrorproof virtueproof weaponproof winterproof