Final answer:
Cardinal Richelieu was the chief minister to King Louis XIII and was instrumental in strengthening the French absolute monarchy by concentrating power in the hands of the king.
Step-by-step explanation:
The cardinal who advised French kings and brought them much power was Cardinal Richelieu. Cardinal Richelieu, serving as the chief minister to King Louis XIII, played a central role in concentrating power in the hands of the king and developing France into an absolute monarchy. This shift in power dynamics notably occurred when the king ceased convening the Estates General, a body that traditionally included representatives of the clergy, the aristocracy, and commoners. Richelieu's influence helped to limit the power of the nobility and strengthen the centralized authority of the monarchy.