Contradiction with Exodus 20:13
"Thou shalt not kill" contradicts the implication in Deuteronomy 21 of taking actions that lead to a death being justified or innocent blood being shed.
Exodus 20:13: Thou shalt not kill.
Contradiction with Matthew 5:44
"But I say unto you, Love your enemies" contrasts with the Old Testament laws that allow for retribution or purification by actions leading to death.
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" contradicts Deuteronomy 21:9 which involves human actions to atone for bloodshed.
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 James 2:13
"For he shall have judgment without mercy, that hath shewed no mercy; and mercy rejoiceth against judgment," which contrasts with the required human action for atonement in Deuteronomy 21:9.
James 2:13: For he shall have judgment without mercy, that hath shewed no mercy; and mercy rejoiceth against judgment. [rejoiceth: or, glorieth]
Contradiction with John 8:7
"He that is without sin among you, let him first cast a stone at her" suggests mercy and introspection contrary to Deuteronomy 21:9's prescribed actions for resolution of guilt.
John 8:7: So when they continued asking him, he lifted up himself, and said unto them, He that is without sin among you, let him first cast a stone at her.