Contradiction with Matthew 5:44
Psalms 129:6 calls for the destruction of enemies, whereas Matthew 5:44 teaches to love your enemies and pray for those who persecute 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 Romans 12:20
Psalms 129:6 implies wishing harm upon adversaries, while Romans 12:20 instructs feeding your enemy if they are hungry and giving them drink if they are thirsty.
Romans 12:20: Therefore if thine enemy hunger, feed him; if he thirst, give him drink: for in so doing thou shalt heap coals of fire on his head.
Contradiction with Proverbs 25:21
Psalms 129:6 suggests adversaries should wither away, contrary to Proverbs 25:21's call to care for one's enemy by providing food and drink.
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 Luke 6:27
Psalms 129:6 speaks of the downfall of enemies, while Luke 6:27 commands to love your enemies and do good to those who hate you.
Luke 6:27: But I say unto you which hear, Love your enemies, do good to them which hate you,