From Vultus Christi:
Concerning the Holy Rosary, once while the priest placed a rosary around the neck of the person who was being exorcised, all of a sudden the demon began crying out, "It is crushing me, it weighs on me, it is crushing me, this chain with the Cross on the end of it." The exorcist exclaimed, "From this day forward this sister of ours will pray the Rosary every day."
Immediately the demon replied, "But you are so few who say it (the Rosary), compared to the whole world!" It is just as well for me that it should be so, because it (the Rosary) harms me. You invoke That One (referring to our Lady), you make me remember the life of That One (referring to the life of Jesus meditated in the mysteries of the Rosary).
Another day, while exorcising the demon, the exorcist pulled a rosary out of his pocket; immediately the demon cried out: "Take away that chain, take away that chain!" "What chain?" "The one with the Cross on the end. She whips us with that chain." This, of course is metaphorical language; it makes us understand, all the same, in very concrete terms, the power of the Rosary and how much the devil fears it.
Translated from Possessioni diabolici ed esorcismo by Father Francesco Bamonte (Paoline, 2006)