Contradiction with Matthew 5:44
Jeremiah 50:9 speaks of assembling nations for battle, whereas Matthew 5:44 teaches to love enemies and pray for those who persecute.
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 Isaiah 2:4
Jeremiah 50:9 talks about going to war, in contrast, Isaiah 2:4 envisions a time where nations will not take up sword against nation and will not learn war anymore.
Isaiah 2:4: And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruninghooks: nation shall not lift up sword against nation, neither shall they learn war any more. [pruninghooks: or, scythes]
Contradiction with Romans 12:19
The verse in Jeremiah calls for attack, but Romans 12:19 advises against taking revenge and leaving room for God's wrath.
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 Exodus 14:14
Jeremiah 50:9 advocates for military action, while Exodus 14:14 suggests that the Lord will fight and people should remain still.
Exodus 14:14: The LORD shall fight for you, and ye shall hold your peace.