In OT, sin refers to transgression. In Paul, sin is something that precedes commands and is discovered by means of the law. Evil desires lead to breaking commandments and rejecting God. Augustine analyzed Pauline link between sin and desire more than any theology had before. Immoderate nature of sinful will corrupts order of nature, putting self in the center and using everything else as means to the self as an end.
Pride is the core of perverted desire.
Love of self equals hatred of God, for it puts self in God's place. Later theology got too hung up on inheritability of original sin. Augustine used anthropology, studied human nature. The universal structure of human conduct is what is passed down from generation to generation. Hegel also started from the self.