Leo Tolstoy
He wrote two of the longest novels in the Western canon, then spent the second half of his life trying to give everything away.
Leo Tolstoy was born in 1828 into Russian aristocracy and died in 1910 having renounced his titles, his copyrights, and most of his possessions. In between he wrote War and Peace and Anna Karenina, which between them cover about as much of human experience as two books can manage.
But Tolstoy was never satisfied with just being a great novelist. He wanted to live correctly — and wrote obsessively about what that meant. His later essays on nonviolence influenced Gandhi directly. His earlier fiction understood something harder: that most of us know what the right thing to do is, and we do the other thing anyway.