דברי הימים ב, פרק כ״א, פסוק י״ג

A harsh indictment is leveled against the king, exposing a deep, twofold corruption that involves both rebellion against God and severe moral crimes against humanity [ביאור שטיינזלץ]. This profound failure is broken down into three major offenses [מלבי״ם].

The first failure is the king's deliberate decision to adopt the corrupt ways of the rulers from the Northern Kingdom. Rather than leading by righteous example, he committed a second grave offense by actively causing the people of Judah to sin, ruining a nation that had remained righteous up until that point. This betrayal involved leading the people astray into idol worship, perfectly mirroring the wicked practices established by the house of Ahab [מצודת דוד].

The third and final crime shifts from spiritual betrayal to a horrific act of violence: the murder of the king's own brothers. These men were fundamentally better than him, and they were killed specifically because they bravely protested and stood in opposition to his evil path [מלבי״ם].