"Do you inquire why, holding these views and possessing some will of my own, I accept so imperfect a proposition? I answer, because I live among men and not among angels; among men as intelligent, as determined, and as independent as myself, who not agreeing with me, do not choose to yield their opinions to mine. Mutual concession, therefore, is our only resort, or mutual hostilities.”
Thaddeus Stevens, a Congressman from Pennsylvania around the time of the Civil War, was one of the greatest statesmen in American history. He was a great orator, fearless abolitionist, and determined reformer.
It may help you to know that he will be played by Tommy Lee Jones in Spielberg's Lincoln.
Lincoln's America was a perfect milieu for him, and Johnson's was not. I think it broke his heart that he had to work under Johnson during Reconstruction, and he went a little crazy. He was so determined to get Johnson impeached that he tried to do so using legal loopholes, and persuasion rather than evidence. He filed impeachment articles 3, maybe 4 times. It's what he's most known for, which is a shame. He should be known for his years of equality-minded legislative work before and during the war, and for his measured view of congressional compromise, as stated above.