The group that best completes the chart is:
C. Ku Klux Klan
The Ku Klux Klan was established in the South around 1866, resisted Reconstruction efforts, used violence to intimidate both African Americans and white allies, and aimed to re-establish white supremacy. The chart compares positive actions of the Freedmen's Bureau with the negative actions of a group like the Klan, making "C" the most fitting choice.