Speculative Catholic offers a traditional prayer for those "difficult people."
from Speculative Catholic
Would it hurt you to say it once?
O Lord God Almighty, I beseech Thee by the Precious Body and Blood of Thy divine Son Jesus, which He Himself on the night before His Passion gave as meat and drink to His beloved Apostles and bequeathed to His Holy Church to be the perpetual Sacrifice and life-giving nourishment of His faithful people, deliver the souls in purgatory, but most of all, that soul which was least devoted to this mystery of infinite love, in order that it may praise Thee therefore, together with thy Divine Son and the Holy Spirit in Thy glory for ever. Amen
A traditional prayer modified (I changed 'most' to 'least')