Idolatry isn't Annulled, even in 1000 times its amount: Pesachim 27b; Temurah 28a
Nullification of the section of hide which idolaters remove from an animal so that its entrails can be removed for idolatrous use [Orot Livuvin]: Temurah 28a
Leaven in a Mixture during and After Pesach: Pesachim 29b-30a