Piss Off Barrett

Piss off Barrett is an achievement in Deus Ex: The Fall.It is earned by countering Lawrence Barrett's criticism for refusing to kill Mikhail Kontarsky.

Walkthrough
While on the Tyrant Jetliner, visit Barrett's room on the lower floor.Talking to Barrett will lead to a brief conversation where he criticizes you for being "gun-shy." Choosing the option to challenge him grants you the achievement.