Mammoth Uncensored Word List:
20 words ending with k, 12 letters long

antikickback bladderwrack chimneystack concertstuck countercheck electroshock gobbledegook gobbledygook groundattack kinnikinnick machtpolitik nonlivestock pressurecook spindleshank splatterpunk straddleback straightneck tiddledywink walkingstick wonderstruck