What are the infamous inventions in history that have not benefited mankind at all?

For example, the melamine in the Sanlu milk powder incident was originally invented to be used in the chemical, plastic and coating industries, which can bring better results in the use of goods, but it was used by people with will and became the chief culprit in hurting children.

Opium, for example, was used to treat diseases a long time ago, and it can bring good curative effect to headaches, strokes, bronchitis and other diseases, but it is also a drug, and many families are fragmented because of it.

For example, radium developed by Madame Curie after tens of thousands of radiation tortures can treat cancer, but in the end it has become the raw material for major countries to manufacture nuclear weapons.