SPOILER WARNINGMission: Operation Blag Flag: Trap is Sprung
At the end of the mission, you will reach Kotch and then interact with him. This will begin his speech. In order to grab this achievement, just use the knife (
) as soon as possible to kill him before he finishes talking. Do not let him finish.
This is also a reference to Jon Snow from Games of Thrones as the character is played by the same actor, and the phrase "You Know Nothing, Jon Snow" is a famous quote from the show.