The hero known for his defeat of a mythical giant is David, who famously slayed the giant Goliath in the Biblical story. David's victory, achieved with just a slingshot and faith, symbolizes the triumph of the underdog against overwhelming odds. This tale has transcended its religious origins to embody themes of courage, faith, and determination. David's battle against Goliath serves as an enduring allegory for overcoming challenges, encouraging individuals to confront their fears and believe in their potential.