What success did Frederick Douglass have in promoting reform?
The largest reform that Douglass pushed for was of course the abolition of slavery, though it is difficult to pin down how much of that was due to his own efforts as there were quite a large number of factors that played a role in that coming to pass. His eloquence and erudition were certainly important in convincing many in the North of the equal nature of African Americans and he certainly played a role in the fight for abolition.
Some of Douglass' success was not immediate so it may be tenuous to give him credit but there are a number of reforms he campaigned for along with of course his great fervor for the abolition of slavery. He was also a great champion of women's rights including suffrage and often spoke in favor of them.