Captain America

Tried to enlist in the Army but was rejected because of his frailty & sickness
Offered the opportunity to take part in a top-secret experiment, Operation Rebirth
Given the Super-Soldier Serum, enhanced his body to the peak of human physicality
Put through an intensive physical & tactical training program; became Captain America
Fought HYDRA during World War II, helped the allies win the war
Lost at sea & frozen in ice in a form of suspended animation
Thawed out in the modern age, joined the Avengers, became their leader