Most Brutal Chapters in our history.
1) Slavery
2) Brutal repression of Native Americans
3) Women's Right to vote
4) Japanese Internment during WWII
5) Nixon's Southern Strategy followed by the Republican descent into a white fascist party
6) Prohibition
#5 is stupidly partisan in what otherwise could be a good discussion.
You left out Jim Crow, and the Chinese Exclusion Act, the Tuskegee experiments.
Women's right to vote- i.e. women's sufferage- is not a 'brutal chapter- but the end of an exclusion that variously excluded blacks and women and non-property owners- I think it was stupid and misguided but not 'brutal'
If we include Prohibition- which I somewhat agree with- then you must include the War on Drugs- since both have had virtually the same deadly effect.