It took 10 plagues to convince Pharoah.
Exodus 8:8 Then Pharaoh called for Moses and Aaron, and said, Intreat the LORD, that he may take away the frogs from me, and from my people; and I will let the people go, that they may do sacrifice unto the LORD. 8:9 And Moses said unto Pharaoh, Glory over me: when shall I intreat for thee, and for thy servants, and for thy people, to destroy the frogs from thee and thy houses, that they may remain in the river only? 8:10 And he said, To morrow. And he said, Be it according to thy word: that thou mayest know that there is none like unto the LORD our God.
Pharoah wanted one more night with the stinking frogs.