Chevrolet Vega
The Vega was one of the first compact cars ever released by General Motors. The styling was meant to be a compact Camaro. The problem was that the performance and reliability were non-existent, and the car lacked any refinement. The Vega was so unreliable that it often broke down after leaving the showroom floor (via Motor Trend).
The Vega has become popular in the aftermarket community as a hot rod. But when it was new, it did nothing but cost GM money. It took years for domestic automakers to figure out how to build a decent subcompact car. The original release of the Vega did the opposite, and despite its popularity on the retro market, it nearly cost Chevrolet their status in the auto world at the time.