Contradiction with Exodus 20:13
The commandment "Thou shalt not kill" could be seen as a contradiction against the acts of war described in Joshua 10:29.
Exodus 20:13: Thou shalt not kill.
Contradiction with Matthew 5:44
Jesus' teaching to "love your enemies" contrasts with the warfare and conquest described in Joshua 10:29.
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
"Vengeance is mine; I will repay, saith the Lord," suggests leaving retribution to God, contrasting Joshua's active role in battles.
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 Isaiah 2:4
The vision of beating swords into plowshares and not learning war anymore stands in contrast to continued warfare in Joshua 10:29.
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 Deuteronomy 20:16-17
These verses command the complete destruction of certain groups, which is a significant aspect of Joshua's campaign; interpretatively, this can be seen as contradictory to the broader Biblical theme of mercy.
Deuteronomy 20:16-17: But of the cities of these people, which the LORD thy God doth give thee [for] an inheritance, thou shalt save alive nothing that breatheth:
Contradiction with James 4:1-2
Suggesting the source of wars is human lusts can be seen as contradicting the idea of divinely sanctioned battles as seen in Joshua 10:29.
James 4:1-2: From whence [come] wars and fightings among you? [come they] not hence, [even] of your lusts that war in your members? [fightings: or, brawlings] [lusts: or, pleasures]