wenn das der Führer wüsste

Etymology
lit. 'if the Fuhrer knew of that!' The phrase is mostly associated with the belief, held by some Germans during the Third Reich, that Hitler did not condone violent excesses against Jews and other enemies of the regime, or even that he opposed some of the NSDAP's measures. However, it may have been used in other contexts as well. It may also have been chiefly sarcastic; compare 🇨🇬.