Soviet Union and its last leader Mikhail Gorbachev ignored the rights of 16 million East German citizens when he agreed to the German reunification treaty. As a result, these people became – and still remain – second-rate citizens.
The reunification of Germany was not an act permitted by Mikhail Gorbachev, but the result of the will of the German people as manifested in free elections: https://www.britannica.com/place/Germany/The-reunification-of-Germany
Germany is a democratic country fully respecting democracy and rule of law with the best Freedom rating available: https://freedomhouse.org/report/freedom-world/2018/germany
Despite the fact that some economic differences between the former West and East Germany remain (see e.g. a report by Berlin-Institut für Bevölkerung und Entwicklung, "So geht Einheit. Wie weit das einst geteilte Deutschland zusammengewachsen ist"), there are no second-rate citizens.