I fell down the philanthropy rabbit hole a few years ago and discovered it's a science. Many , many, many attempts at good have been pure evil historically because amateur philanthropists didn't do their research into this complex field. A pure heart and good actions can be diabolical.
This could range from mundane things like you or I donating to homeless man that uses the funds for his final overdose, or alternatively large scale incidents. Two large scale incidents come to mind. First example is the red cross allowing blood/plasma donations for sale in the 70s and 80s only for disease infested drug addicts with no other income stream to be primary donors. Second example would be numerous charities distributing insect nets in hopes of stopping malaria in the Great lakes region of Africa and West African river basins, only for these same people to have the higher malaria rates years later cause these bed nets make excellent fishing nets. And Unbeknownst to these fishermen, they have just added toxic chemicals from the nets to their main food source.