Stalin - Before the
dissolution of the Soviet Union and the archival revelations, some historians estimated that the numbers killed by Stalin's regime were 20 million or higher
Mao - Mao's policies were responsible for a vast number of deaths, with estimates ranging from 40 to 80 million victims due to starvation, persecution, prison labour, and mass executions
Pol Pot - Estimates range from 1.5 to 3 million people/citizens of Cambodia having died at the hands of the Khmer Rouge, with the consensus being approximately 2 million, nearly 25% of Cambodia's population in 1975 ( c. 7.8 million).
Kahn - estimated to have killed 40-60 million people (11% of the worlds population at that time)
Hitler - 19.3 million killed
Idi Amin - 500,000 killed
Leopold II - 10 million killed
In the US - Andrew Jackson's forced migrations were the direct cause of up to 16,000 Native American deaths and a slave owner.
Roosevelt imprisons 122,000 Japanese Americans solely due to their race during WWII
I could add in current political leaders who have/are allowing genocide to take place if you like. Is Trump really worse than Putin? Than Jinping, than Kim Jong Un? And many more.
But we all have opinions and the right to have that opinion. I would certainly disagree with your thoughts on this one. I would also disagree that 'not conceding a legitimate election differentiates us from the world". I might be misunderstanding what you meant by this.