Stop apologizing for post length, or I'll find a way to instate a minimum character limit for your posts.
Also, in the same vein as SoB above, Drachen Fire at Busch Gardens Williamsburg/Europe definitely ranks up there. A huge ride designed for a B&M-style structure and built by Arrow, what could possibly go wrong? Especially considering that Arrow decided to give the B&M-style structure a try, despite never having built anything like it before? Add to this a few revolutionary new elements that should have warranted both computer-assisted profiling and precision track manufacturing in a time where neither of those were available, and the end result was a messed-up ride that stood for six years (give or take some downtime to remove the first inversion), rode as rough as a cheese grater, pushed Arrow towards bankruptcy, and had its reputation ruined by word-of-mouth more than a decade before social media went mainstream. I'd go into more detail, but I couldn't possibly do a better job of it than Defunctland:
In a similar vein, the fate of Six Flags Astroworld was one mighty flop too, and unlike other examples in this thread, it involved the entire theme park. Six Flags was losing money, the property Astroworld sat on looked like it could bring in a fortune if sold for development, and it turned out not to. The whole park was bulldozed to the ground, the land was sold at a fraction of the projected price, and now it just sits there empty while Houston has become the biggest US city to not have any proper amusement parks nearby. And Six Flags had to file for bankruptcy too. Defunctland tells that whole story too, just watch the video above and it will probably appear among the suggested videos to watch next.
