Believe in a Hero
From Halopedia, the Halo wiki
Believe in a Hero is an achievement in Halo: Combat Evolved Anniversary and Halo: The Master Chief Collection. It is awarded for completing the campaign on Heroic. It is worth 20 Gamerscore. Earning the achievement also unlocks the "Birth of a Spartan" achievement if the player hasn't completed the campaign on Normal.
In the original game, it is represented by the difficulty shield with a single M41 rocket launcher over it, however the The Master Chief Collection Steam achievement art is of the well-known crossed swords. The Xbox art it is represented by concept art for The Pillar of Autumn.