Contradiction with 1 Kings 15:5
This verse states that David did what was right in the eyes of the Lord, except in the matter of Uriah, whereas 2 Kings 14:3 mentions that Amaziah did what was right like his father Joash, but not like David, suggesting David's standard was superior.
1 Kings 15:5: Because David did [that which was] right in the eyes of the LORD, and turned not aside from any [thing] that he commanded him all the days of his life, save only in the matter of Uriah the Hittite.
Contradiction with 2 Chronicles 25:2
This verse says Amaziah did what was right but not with a perfect heart. In contrast, 2 Kings 14:3 states Amaziah followed his father Joash in doing right, implying a more favorable view.
2 Chronicles 25:2: And he did [that which was] right in the sight of the LORD, but not with a perfect heart.
Contradiction with 2 Kings 12:2
This verse notes that Joash did what was right all his life because Jehoiada the priest instructed him. This sets a precedent that contradicts 2 Kings 14:3's implication that Amaziah was less perfect than David.
2 Kings 12:2: And Jehoash did [that which was] right in the sight of the LORD all his days wherein Jehoiada the priest instructed him.
Contradiction with 1 Kings 11:6
This verse states that Solomon did evil in the eyes of the Lord, unlike David his father, contradicting the portrayal of Amaziah as doing right yet not like David, who was faultless except in one matter.
1 Kings 11:6: And Solomon did evil in the sight of the LORD, and went not fully after the LORD, as [did] David his father. [went...: Heb. fulfilled not after]
Contradiction with 1 Kings 3:14
God tells Solomon to walk in David's ways to have a prolonged reign, implying David's ways were fully right, while 2 Kings 14:3 suggests Amaziah did not reach David's level of righteousness.
1 Kings 3:14: And if thou wilt walk in my ways, to keep my statutes and my commandments, as thy father David did walk, then I will lengthen thy days.