Contradiction with Hebrews 10:17
This verse states that God will not remember sins, which may seem contradictory to the notion of sins being forgiven because it implies sins were remembered before.
Hebrews 10:17: And their sins and iniquities will I remember no more. [And their: some copies have, Then he said, And their]
Contradiction with Matthew 6:15
This verse suggests unforgiven sins if we do not forgive others, which contradicts the assurance of forgiveness given in 1 John 2:12.
Matthew 6:15: But if ye forgive not men their trespasses, neither will your Father forgive your trespasses.
Contradiction with James 2:24
This verse emphasizes justification by works, which could be seen as contradicting the notion of unconditional forgiveness in 1 John 2:12.
James 2:24: Ye see then how that by works a man is justified, and not by faith only.
Contradiction with 2 Corinthians 5:10
This verse talks about receiving according to one's deeds, potentially contradicting the idea of forgiveness as stated in 1 John 2:12 without prerequisites.
2 Corinthians 5:10: For we must all appear before the judgment seat of Christ; that every one may receive the things [done] in [his] body, according to that he hath done, whether [it be] good or bad.