Rode roughshod over the constitution, suspended civil liberties with draconian whim, and regarded blacks as a "nuisance"
That being said, his task was to preserve the Union, and win the war, and he accomplished that. Ignoring some of his methods, this was an honorable task, albeit not always accomplished in an honorable way.
I suspect that he would have corrected the constitutional and legal violations that he created in his second term, but the cavalier ease with which he instituted them has always troubled me.