Hunter Hunted (Fallout 4)

Hunter/Hunted is a quest and achievement/trophy in Fallout 4.

Quick walkthrough
Travel to C.I.T., track and kill the Courser in order to take his chip.

Detailed walkthrough
Upon getting the quest, travel to the C.I.T. ruins north of Diamond city. The "Courser Signal" will be available on the Pip-Boy's radio at that point, tune to it and follow the signal east to Greenetech Genetics.

Greenetech is filled with Gunners who are fighting the Courser. As you enter the building, the commander of the Gunners starts issuing orders over the intercom; he orders half of his troops to retreat up the building as the Courser advances on them and the other half to engage you. However, the majority of the Gunners assets will be thrown at the Courser. You have to fight your way up through the building. The Courser is just ahead of you the whole time, though he easily eliminates his opposition, littering his road with Gunner bodies.

Reaching the fifth floor, you will hear a salvo of explosions - missiles are being fired at the Courser (who shrugs them off). These explosions will not affect you. Once you get to the seventh floor, there is an elevator that takes you up to the top of the building.

Once there, the Courser can be heard threatening some Gunners for a password - one refuses to give it to him and will be executed. You may intervene in time to prevent the rest of the Gunners to be killed. Approach him and he'll ask what you want, shortly afterwards he will engage unless you got his deactivation code from Mama Murphy. Once the fight is over, you can loot the Courser chip off his body and the quest is complete.

After the fight, you can see a woman locked in the room that the Courser was trying to gain access to. She asks you to retrieve the password to the door that one of the Gunners stashed in a nearby toolbox. Once she is let out, she reveals that she is a Synth and tells you that the Courser was after her and the Gunners caught her as she traveled across the Commonwealth. She will request to leave and will never be seen from again.

Any Gunners that were not yet executed by the Courser will plead for you to spare them, there are no interactions with them otherwise.