Contradiction with Exodus 34:7
Exodus 34:7 states that God keeps mercy and forgives, which may contrast with Isaiah 65:15's idea of leaving a curse behind.
Exodus 34:7: Keeping mercy for thousands, forgiving iniquity and transgression and sin, and that will by no means clear [the guilty]; visiting the iniquity of the fathers upon the children, and upon the children's children, unto the third and to the fourth [generation].
Contradiction with Numbers 23:19
Numbers 23:19 emphasizes that God does not lie or change His mind, which contrasts with Isaiah 65:15's implication of a change in stance towards the servants.
Numbers 23:19: God [is] not a man, that he should lie; neither the son of man, that he should repent: hath he said, and shall he not do [it]? or hath he spoken, and shall he not make it good?
Contradiction with 1 John 1:9
1 John 1:9 speaks about forgiveness and cleansing from unrighteousness, which may contradict the notion of permanent name-cursing in Isaiah 65:15.
1 John 1:9: If we confess our sins, he is faithful and just to forgive us [our] sins, and to cleanse us from all unrighteousness.
Contradiction with Romans 8:1
Romans 8:1 mentions no condemnation for those in Christ, possibly opposing Isaiah 65:15's implication of enduring curses for previous actions.
Romans 8:1: [There is] therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.