Inventions that were worst for the world, for the most part, are all things created with good intentions that have changed the world for eternity. While few inventions are perfect, these stand out as among the best that created the worst outcomes. These are not just products nobody needs these are inventions that made the world a worse place to live.
Few can deny that the invention of automobiles and airplanes made traveling much more efficient but it's hard to forget that cars pollute the earth and airplanes can be used for terrorism or war. The same goes for rockets. They launched people into space but also carried nuclear weapons that caused mass destruction. Television and the Internet changed how we interact and share information, but sitting in front of a computer monitor or TV for countless hours, along with corn syrup, isn't helping fight obesity. Nuclear fission creates power but can also wipe entire populations off the globe when used for evil.
Then there are other inventions where it's hard to find a benefit. Cigarettes are a proven cause of death in roughly half who smoke. How many other products that are so widely used can say the same? Along the same lines, there is very little good to say about gas chambers whose sole purpose is to kill humans and animals.Unlike the most useless inventions which aren't so much harmful as they are just plain dumb, these inventions changed the course of history forever and are thought of by many as the worst inventions of all time. Think of a world with no gun deaths had gun powder never been invented or a history with no slavery or Civil War had the cotton gin never been created. That's not a bad reality to consider.