One of the most useful German nouns is the Swiss[ᵈᵘᵇⁱᵒᵘˢ][ᵈⁱˢᶜᵘˢˢ] coinage "Verschlimmbesserung", which is a portmanteau of Verschlimmerung (deterioration) and Verbesserung (improvement) and describes the act of making something worse in an attempt to make it better.

If your language has an equivalent expression, please share and explain it below.

Boosts for reach appreciated!