Lincoln

Although not a president yet, Abraham Lincoln was never a pro-slave politic.
" A house divided against itself cannot stand... this government cannot endure permanently, half slave and half free." 
Abrahan Lincoln becomes president in a critical time in which the nation is divided over slave and free states. The Southern States, or the slave states, did  not want the free states to have more power than them. They also didn't want to lose the power over the slaves which they knew eventually would happen if they remained under the United States of America. They tried to secede from the nation and this led to the American civil war.

 "without slavery the rebellion could never have existed; without slavery it could not continue"

Abraham Lincoln decides to give freedom to all slaves in the nation to gain more support and therefore regain control over the southern states. Eventually they would regain the power and have the 13, 14 and 15 amendment passed. They respectively, banned slavery, defined citizenship and gave the right to vote to black men.
Lincoln even tough against slavery he was fine with the idea of "separate but equal". He thought the races to be better off separated and he criticized the amalgamation of the races that slavery had created. If there was no slavery there wouldn't have a mixing of races.

He was definitely a very important character in American history, and the one responsible for ending  slavery, however his views towards social inequality does not satisfy his views over slavery.