Which was worse? Holocaust, US Slavery, or Native American policies?

The holocaust lasted from the early 1900s to 1945 and resulted in the deaths of 11 to 17 million people.

Slavery killed some 60 million (?) Africans/African Americans, it lasted for many generations (1500s to 1865), and the negative residual affects can still be felt to this day.

Westward expansion and the destruction of Native Americans resulted in nearly the entire history and knowledge of Native Americans erased.