Contradiction with Psalm 34:13
Encourages to keep the tongue from evil, whereas Proverbs 24:2 mentions those whose heart studies destruction and their lips talk of mischief.
Psalm 34:13: Keep thy tongue from evil, and thy lips from speaking guile.
Contradiction with Matthew 5:9
Blessed are the peacemakers, in contrast to Proverbs 24:2 which speaks of people whose heart devises destruction.
Matthew 5:9: Blessed [are] the peacemakers: for they shall be called the children of God.
Contradiction with Romans 12:21
Advises not to be overcome by evil, but overcome evil with good, contradicting Proverbs 24:2's focus on plotting destruction.
Romans 12:21: Be not overcome of evil, but overcome evil with good.
Contradiction with James 3:10
Out of the same mouth proceeds blessing and cursing, which contrasts with Proverbs 24:2's mention of lips talking mischief.
James 3:10: Out of the same mouth proceedeth blessing and cursing. My brethren, these things ought not so to be.
Contradiction with 1 Peter 3:10
Whoever would love life must keep their tongue from evil, contradicting Proverbs 24:2's discussion of speaking mischief.
1 Peter 3:10: For he that will love life, and see good days, let him refrain his tongue from evil, and his lips that they speak no guile: