The QL (Quantum Leap) was supposed to be the successor to the hugely popular ZX Spectrum computer. It was a rather powerful and advanced machine for its day, especially at its price range. In fact, it was the first personal computer with preemptive multitasking. However, Sinclair completely fucked up its launch. They announced it to be going into production and took orders when there was not even a finished prototype. As the machine was rushed to completion, the original firmware was full of bugs, and the much-touted Microdrive had serious reliability issues. The QL also lacked any form of backwards compatibility with the ZX.
When Amstrad bought near-bankrupt Sinclair, they kept producing the ZX, but promptly killed the QL.
Curiously, this failure led to a great creation: a young nerd from Finland made the mistake of buying a QL, and due to the lack of commercial support, he had to write his own software. Many years later, when he couldn't afford Unix for his PC, he kept that punk "do it yourself" attitude and wrote his own Unix clone... Linus' Unix.