Contradiction with Matthew 5:44
1 Samuel 20:25 depicts Saul's growing animosity and concealment of intent, while Matthew 5:44 encourages love and prayer for one's enemies.
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 1 John 2:10
Unlike Saul's hostility in 1 Samuel 20:25, 1 John 2:10 advocates living in love and not causing others to stumble.
1 John 2:10: He that loveth his brother abideth in the light, and there is none occasion of stumbling in him. [occasion...: Gr. scandal]
Contradiction with Proverbs 15:1
1 Samuel 20:25's setting preludes conflict, whereas Proverbs 15:1 advises gentle speech to defuse anger.
Proverbs 15:1: A soft answer turneth away wrath: but grievous words stir up anger.
Contradiction with Romans 12:17
Saul's premeditated actions in 1 Samuel 20:25 hint at revenge, contrasted by Romans 12:17's counsel against repaying evil for evil.
Romans 12:17: Recompense to no man evil for evil. Provide things honest in the sight of all men.
Contradiction with 1 Corinthians 13:4-5
Saul's behavior in 1 Samuel 20:25 is opposite to the love described in 1 Corinthians 13:4-5, which is patient and kind without envy.
1 Corinthians 13:4-5: Charity suffereth long, [and] is kind; charity envieth not; charity vaunteth not itself, is not puffed up, [vaunteth...: or, is not rash]