Contradiction with Exodus 20:13
Joshua 12:16 lists slain kings, contradicting the commandment "Thou shalt not kill."
Exodus 20:13: Thou shalt not kill.
Contradiction with Matthew 5:44
Jesus' teaching to "love your enemies" contrasts with the conquest and defeat described in Joshua 12:16.
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
The vision of nations not learning war contrasts with the acts of war involving slain kings in Joshua 12:16.
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]