Contradiction with Matthew 5:9
Isaiah 11:14 describes a conquest over enemies, while Matthew 5:9 emphasizes peacemaking.
Matthew 5:9: Blessed [are] the peacemakers: for they shall be called the children of God.
Contradiction with Romans 12:17
Isaiah 11:14 depicts vengeance, whereas Romans 12:17 advises against repaying evil for evil.
Romans 12:17: Recompense to no man evil for evil. Provide things honest in the sight of all men.
Contradiction with Matthew 5:44
Isaiah 11:14 involves defeating enemies, in contrast to Matthew 5:44, which teaches to love and pray for enemies.
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 12:19
Isaiah 11:14 speaks of taking action against foes, as opposed to Romans 12:19, which instructs to leave vengeance to God.
Romans 12:19: Dearly beloved, avenge not yourselves, but [rather] give place unto wrath: for it is written, Vengeance [is] mine; I will repay, saith the Lord.
Contradiction with Luke 6:27
Isaiah 11:14 involves overcoming adversaries, whereas Luke 6:27 encourages loving those who oppose you.
Luke 6:27: But I say unto you which hear, Love your enemies, do good to them which hate you,