Answer: Ajatashatru
Notes: Ajatashatru was the son of King Bimbisara and was a contemporary of both Mahavira and Gautama Buddha. He forcefully took over the kingdom of Magadha from his father and imprisoned him. He followed policies of conquest and expansion. He defeated his neighbours including the king of Kosala, then, He occupied Kashi and captured the smaller kingdoms. Because of his policies, Magadha became the most powerful kingdom in north India under his reign.
