Final answer:
Harriet Tubman demonstrated exceptional courage by repeatedly risking her life to lead over three hundred enslaved individuals to freedom via the Underground Railroad.
Step-by-step explanation:
The best example of Harriet Tubman's courage is highlighted through her perilous and repeated journeys into the South to liberate enslaved individuals. In Sarah H. Bradford's text, it is mentioned that Tubman 'returned to the South thirteen times to help over three hundred other freedom-seekers through the Underground Railroad to liberty in the North.' This brave and selfless act of risking her own life to free others demonstrates an unparalleled level of heroism and dedication to the abolitionist cause, setting a profound example for posterity.