ESV: He struck down all the firstborn in their land, the firstfruits of all their strength.
NIV: Then he struck down all the firstborn in their land, the firstfruits of all their manhood.
NASB: He also fatally struck all the firstborn in their land, The first fruits of all their vigor.
CSB: He struck all the firstborn in their land, all their first progeny.
NLT: Then he killed the oldest son in each Egyptian home, the pride and joy of each family.
KJV: He smote also all the firstborn in their land, the chief of all their strength.
NKJV: He also destroyed all the firstborn in their land, The first of all their strength.