You obtain the Good Samaritan achievement in Death Stranding by delivering your first of any lost cargo packages to their proper location.
Good Samaritan Achievement
At the beginning of the game when you’re picking up the deliveries for a specific quest to Central Knot City, there are other packages that are noted as lost cargo. These don’t pertain to any kind of specific order that you’ve been told to do, but are either dropped by other players or are randomly placed around the world.
You’ll need to grab them, and then find where they need to be delivered to.
This achievement will be gained at some point in the game, but it doesn’t have to be at the start. You can get away with not picking up any packages but the ones you need in order to progress the storyline.
But eventually, you’ll pick up a lost cargo and deliver it. Once you confirm the cargo, you’ll gain the achievement Good Samaritan.