Contradiction with 1 Thessalonians 5:16
Psalms 129:8 speaks of a lack of blessings, contrasting with the call to "rejoice evermore" in 1 Thessalonians 5:16.
1 Thessalonians 5:16: Rejoice evermore.
Contradiction with Matthew 5:44
While Psalms 129:8 discusses absence of blessings for enemies, Matthew 5:44 teaches to bless those who curse you.
Matthew 5:44: But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you;
Contradiction with Proverbs 25:21
Psalms 129:8 implies withholding blessings, while Proverbs 25:21 advises feeding and giving drink to your enemy.
Proverbs 25:21: If thine enemy be hungry, give him bread to eat; and if he be thirsty, give him water to drink:
Contradiction with Romans 12:14
Psalms 129:8 hints at withholding blessings, whereas Romans 12:14 instructs to bless and not curse persecutors.
Romans 12:14: Bless them which persecute you: bless, and curse not.