Is there a name for this specific concept? Where somebody invents something (to do them good) but then that thing turns around and backfires on them?
There’s the phrase “Hoist by their own petard” but not sure if that’s specific enough to inventions, probably not.
I really hope there’s a single word for it out there… more convenient yanno.
There’s probably a German word for the concept that there is a German word for everything.
A “Thomas Midgley Jr.”
Alfred Nobel might be considered a runner up, but I feel he recovered his reputation. That and I don’t think anyone but himself really was upset with the path his invention took.
I know you wanted a word, but I nominate “Midgley” to be the new word for that. “To midgley something” is to attempt to create something of value that instead only makes things worse. It’s an improvement in the negative direction.