The achievement is unlocked when you complete the first of four possible endings. It is story related and cannot be missed. The four endings can be played in any sequence and the achievement pops when you conclude the first ending you select.
To have the option of playing all four endings without retracing the entire story, make sure you make hard saves at the beginning of the
Red Tape of Command mission and the beginning of the
Ambrose Intersection mission. Note that you can get all ten of the DLC's achievements by doing only three of the four endings. Consult the spoiler sections to see how this can be done.
The four endings are:
*** Spoiler - click to reveal ***1. Achieve a compromise leading to the Family Reunion achievement
2. Take Minnie's side by activating the reactor leading to the Greenlight protocol achievement. However, the achievement can be earned elsewhere so this ending is not required for a 100% completion.
3. Take Olivia's side by destroying the synthesizer leading to the NDA protocol achievement.
4. Take neither Minnie's nor Olivia's side. Kill Minnie before you acquire the journal, causing Lucien to appear. Activate the reactor leading to the Greenlight protocol achievement and deliver the journal to him leading to the Postman achievement.
The most efficient path to get the four achievements associated with each ending:
*** Spoiler - click to reveal ***- When the Red Tape of Command Mission starts, make a hard, manual save. Make sure it is BEFORE you get the journal. This is the main branch point.
- Play through to the Postman achievement. You will also get the Greenlight protocol along this path. The following is a detailed guide: Solution for The Postman In The Outer Worlds
- Load the hard, manual save you made BEFORE picking up the journal. Go directly to the SMC and pick up the journal.
- Upon returning to your ship, ADA will patch you through to a conversation. This concludes the Red Tape of Command Mission and automatically initiates the Ambrose Intersection main quest.
- Use this guide to unlock the NDA Protocol achievement: Solution for NDA Protocol In The Outer Worlds. Revert to a manual or auto-save created BEFORE you executed the NDA protocol.
- Play through to the Family Reunion achievement. The following guide provides a detailed solution: Solution for Family Reunion In The Outer Worlds
- You have now triggered all 4 endings using only 2 branches