The Embraer EMB-120 Brasilia
The Brasilia had a shaky and unreliable turboprop engine. One day, it broke into pieces mid-flight. Fourteen people perished in the accident. The Brasilia's track record is scary at best and is considered one of the biggest mistakes of passenger airlines. Somehow, it still operates as a freight plane!
The B.E. 9
The B.E. 9 came to fruition in the midst of World War I. It was under the strict supervision of the British Royal Flying Corps. It had machinegun capabilities that were dangerous for enemies and the passengers of the plane. Too many times, the machine guns completely tore apart the plane's own propellors. It wasn't in service for very long.