[pseudohadamard]

Also, Christianity at least has never been truly monotheistic. For example the Second Council of Constantinople (I think that was the one) had to go in and weed out the great mass of pre-Christian cruft that had been snuck back in, old Babylonian and Hebrew supernatural entities cunningly disguised as "angels", and then more recently you've got the global veneration of Mary and, although this has mostly faded in the last 100 years, saints, also serving the role that lesser gods served in other religions but carefully fitted up to not make it heresy.

Islam, from my limited knowledge, does seem to be purely monotheistic despite at least one attempt to reconcile with followers of the goddesses Lat, Uzza, and Manat.