(Then Cardinal) Ratzinger in his 1968 book Introduction to Christianity, pp. 339-340, cites the 13th century theologian William of Auvergne as follows on the sinfulness of the Church: “We are no longer dealing with a bride, but with a monster or terrible deformity and ferocity.” The reference he gives for the citation is Von Balthasar’s Explorations in Theology, Vol. 2: The Spouse of the Word, pp. 193-288, esp. 194-197.
I don’t have the book, and I’ve not read anything of consequence by or about William of Auvergne. But considering that he’s 13th century, I think this is definitely something to follow up on.