“You are honestly telling me that Jesus supported slavery?”
You mentioned it a being a great sin. I simply asked you for a source making that case.
The Bible in the New Testament neither advocates slavery as a positive good nor opposes it as an evil. It merely takes it for granted as a fact of life.
In the Old Testament slavery is also treated as a fact of life, and in fact its position on the subject is very nearly identical to that of the Koran. Except for the sabbath year and Jubilee laws, which did not apply to slaves except those of Hebrew birth, and were probably never really applied anyway.
The principles of human equality and all of us being children of God lead by logical extrapolation to abolitionism, but that principle as such is just not found explicitly in the Book.
So, IMO, it is not possible to say that slavery is a sin per the Bible. But then if we take all parts of the Bible literally we can’t wear clothes of blended fibers or eat lobster, and we must not suffer a witch to live.