Does Japanese have a term more-or-less equivalent to the German Klugscheißer (literally, "clever-shitter"; in English: smartypants, smartass, know-it-all, etc.)?
(Needless to say, this is not a term suitable for polite conversation!)
The best I could do was to look for translations for "smartass" or "smartypants". All I got this way was 賢い人, which, AFAIK, is not considered particularly vulgar, and does not even carry the derogatory/mocking overtones of the Klugscheißer. (But please correct me if I'm wrong!)
P.S. If you found an online source for this translation, please include it in your answer! I had no success with the many I tried, including a short video entirely devoted to equivalents in various languages (but not in Japanese).