Contradiction with Exodus 20:13
"Thou shalt not kill" is often seen as a command against taking life, whereas 1 Kings 2:38 indirectly relates to commands surrounding executions by extension of Solomon's orders.
Exodus 20:13: Thou shalt not kill.
Contradiction with Matthew 5:44
Jesus' teaching to "love your enemies" contrasts with the narrative action of dealing harshly with adversaries in contexts like that of 1 Kings 2:38.
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, which can conflict with the directive atmosphere around dealing with enemies in 1 Kings 2:38.
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.