In the commentary of the holy Rabbi Yaakov Yitzchak of Biala on the Haggadah, it is explained that each plague that struck the Egyptians instilled a positive trait in the hearts of the Israelites.

The plague of blood cooled the heat of lust and evil desire from the bodies of the Israelites.

The plague of frogs instilled in them the willingness to sacrifice themselves for His name with love, just as the frogs did.

The plague of lice instilled in them complete faith that the Holy One, blessed be He, sustains and provides for all from the horns of wild oxen to the eggs of lice.

The plague of wild beasts instilled in them the attribute of unity, just as the different kinds of animals united to do the will of their Creator.

The plague of pestilence instilled in them the fear of Hashem, for it became known to them that just as one cannot live with polluted air but needs clean air every moment, so too one cannot live a moment without His vitality.

The plague of boils instilled in them the attribute of shame, just as the magicians were ashamed to stand before Moshe.

The plague of hail instilled in them the constant hope to never despair of mercy, even if a sharp sword is placed, etc., just as the hail that was already on its way down stopped and did not hit the ground (Tanchuma Va'era 16).

The plague of locusts instilled in them the belief that Hashem created the entire world ex nihilo, just as the plague of locusts came ex nihilo, as it is written (Exodus 10:14), "Before them there were no [locusts] like them."

The plague of darkness accompanied all the plagues, meaning that even though they were struck, their eyes were not opened to see the providence of Hashem, and only the Israelites had light in their dwellings, which brought them to the attribute of wisdom, and they merited to see the power and greatness of the Almighty.

The plague of the firstborn was the final blow, meaning that it nullified all the power and root of Egypt, and through this, the Israelites reached their original level, the aspect of the will in creation and the thought of Israel that preceded the world, and the supreme intellect was awakened in them [see Likutei Yehuda Shemot page 43 for what is written about this in the name of Chidushei HaRim].