How did violence and Jim Crow laws undermine the promises of Reconstruction?

Reconstruction was the period between the end of the Civil War in 1865 and 1877, when the Democrats returned to power in the southern states. During this period, Republicans tried to guarantee a whole series of civil and political rights to African Americans, such as citizenship, the right to vote, and social equality against whites.

But when Reconstruction ended, all the advances in this regard were put aside by the Democrats, who established a segregation system based on the Jim Crow Laws, which, although they guaranteed African Americans certain rights (since they were established in the 13th, 14th and 15th Amendments to the Constitution), made them inaccessible and of much lower quality than those of the whites. In addition, a series of mechanisms of institutional violence were established, such as the Klu Klux Klan, through which African Americans were even more limited in their rights.

b - those executed came from every social and economic class