greatest hero of the age; mastermind of the era
A literary, somewhat dramatic expression for a person who dominates their time through talent, achievement, or influence. Often used in historical or biographical contexts.
He was truly a person worthy of being called the greatest hero of his age.
Oda Nobunaga, the mastermind of the Warring States period.
A fixed Sino-Japanese compound: 一世 (one generation/era) + の (possessive particle) + 雄 (hero/leader). The expression is literary and has been used since at least the Meiji period.