I say Stalin killing his own countrymen he killed so many people in his own country, the fact that it was his own country is what makes it extra bad.
What you said is actually what genocide is, it's not "extra bad" but simply what the word means.
*Quote - "Genocide is generally considered one of the worst moral crimes a government (meaning any ruling authority, including that of a guerrilla group, a quasi state, a Soviet, a terrorist organization, or an occupation authority) can commit against its citizens or those it controls."
It was of course Hitler and his attempt to murder all Jews that broadened the words meaning to include outside groups.
*Quote - "The major reason for this is what the world learned about the Holocaust, the systematic attempt of German authorities during World War II to kill all and every Jew no matter where found-to destroy Jews as a group. This murder of between 5 to 6 million Jews became the paradigm case of genocide and underlies the word's origin."
If you wish to consider the worst as the highest amount then:
*Quote - " Taking both social definitions into account, governments have murdered probably around 174 million people during the 20th Century. Most of this killing, perhaps around 110 million people, is due to communist governments, especially the USSR under Lenin and Stalin and their successors (62 million murdered), and China under Mao Tse-tung (35 million). Some other totalitarian or authoritarian governments are also largely responsible for this toll, particularly Hitler's Germany (21 million murdered) and Chiang Kai-chek's Nationalist government of China (about 10 million). Other governments that have murdered lesser millions include Khmer Rouge Cambodia, Japan, North Korea, Mexico, Pakistan, Poland, Russia, Turkey, Vietnam, and Tito's Yugoslavia."
*Quotes taken from
Chalk, F., and K. Jonassohn. The History and Sociology of Genocide: Analysis and Case Studies, New Haven 1990.
