I don’t know if he was a war criminal, but he was notoriously racist. He “freed” the slaves for his politics, not for his want of equality for men of all races. A google search will easily take you to a list of quotes from him regarding his position on “negroes,” but here’s probably the one that is most well known:
“I will say then that I am not, nor ever have been in favor of bringing about in anyway the social and political equality of the white and black races – that I am not nor ever have been in favor of making voters or jurors of negroes, nor of qualifying them to hold office, nor to intermarry with white people; and I will say in addition to this that there is a physical difference between the white and black races which I believe will forever forbid the two races living together on terms of social and political equality. And inasmuch as they cannot so live, while they do remain together there must be the position of superior and inferior, and I as much as any other man am in favor of having the superior position assigned to the white race. I say upon this occasion I do not perceive that because the white man is to have the superior position the negro should be denied everything.”
As far as the rest of his presidency, I’d say he was fair.