Some off-the-cuff examples that come to mind:

- Drastic overregulation of nuclear energy in the US, resulting in fossil-fuel pollution measurable in gigatons over the past several decades accompanied by literally countless illnesses and premature deaths.

- Premature mandates for airbags in cars that resulted in hundreds of needless child deaths because the technology wasn't yet safe enough for universal deployment. A scenario that's playing out right now with misfeatures like automated emergency braking.

- The Jones Act (Merchant Marine Act of 1920), whose effects are too convoluted to go into here.

- Misguided, market-distorting housing policies, ranging across the spectrum from rent control to Proposition 13.

- Many if not most aspects of the War on Drugs, including but not limited to mandatory minimum sentencing and de-facto hardwiring of racial bias into the justice system.