Original: This has happened just twice, both times in the 1950s: the Socialist Reich Party (Sozialistische Reichspartei, SRP), an outright neo-Nazi party, was banned in 1952, and the Communist Party of Germany (Kommunistische Partei Deutschlands, KPD) was banned in 1956.
Simplified: This has only happened twice, both times in the 1950s: the Sozialistische Reichspartei (SRP), was a neo-nazi party. The Communist Party of Germany (KPD) was banned in 1956.