What did King Manasseh do with his own son?

Answer: Made him pass through the fire

Manasseh sacrificed his own son in the fire (KJV: made him pass through the fire), practiced sorcery and consulted mediums.

“He sacrificed his own son in the fire, practiced sorcery and divination, and consulted mediums and spiritists. He did great evil in the sight of the LORD, provoking Him to anger.”— 2 Kings 21:6 (BSB)