The Compromise of 1877 was the compromise that ended Reconstruction. It represents a betrayal of African Americans. It represents a time when the United States decided that black rights were not important enough to fight for.
By 1877, Reconstruction had lost its popularity. Most of the whites in the South had always hated it. They felt they were being ruled by foreign occupiers. Many in the North were uncomfortable with it. They felt, with good reason, that it was anti-American to deny democracy to American citizens. They did not like the idea of having to use the military to enforce Reconstruction on the South.
Moreover, whites in the North did not really think there was much point to Reconstruction. The only thing that Reconstruction was doing by this point, it seemed, was protecting the rights of the African Americans in the South. Most Northerners did not really care about the rights of African Americans. Therefore, they did not think it was right to impose military rule on the South just for the sake of the African Americans.
Therefore, the Compromise of 1877 became possible. The Republicans were willing to end Reconstruction in return for having Rutherford B. Hayes win the presidency. This can be seen as a betrayal of black Americans in the South.