One life was given to save mankind from eternal destruction: the life of the greatest man who ever lived, Jesus Christ.
Many today don't care about him, not even realizing that his life affects each of us. What he did is the grandest expression of love in the whole universe. It's the LOVE of our Almighty God and Creator, and of his only-begotten Son.
An in-depth examination on how Jesus' life affects us can be read here:
Reliving Jesus' Last Days on Earth