Ten times Pharaoh said no

Let my people go. Pharaoh's answer is to double the workload, and the Hebrews' first response to Moses is to blame him for making things worse. Then the plagues come, one after another, and they are not random cruelty: each one strikes at something Egypt worshipped — the Nile, the sun, the livestock, and finally Pharaoh's own son, who was held to be divine. It is a contest between gods, fought in public, and the God of slaves wins every round. Pharaoh bends and then hardens, bends and then hardens, nine times — a man destroying his own country rather than admit he is not in charge of it. Exodus is unblinking about the cost. It is also clear that the alternative was leaving a whole people in chains for ever.