How did Frederick Douglass challenged the power of slave owners?

Fredrick Douglass was a formerly enslaved man who became a public speaker, activist and author. Douglass became a leader of a movement, (the abolitionist movement), which sought to end slavery. He taught the other slaves around him how to read using the bible against the wishes of his ‘owners’.
Later on Douglass attended abolitionist meetings in which he shared his story of slavery and escape.
Finally (but not all) Frederick also published his autobiography which talked about the time he spent as a slave. This helped raise awareness of the atrocities of slavery to people who might not of known or didn’t know the full extent of it, challenging the power of slave owners.