Gears of War 2
79 Achievements
1750
107-134h
Xbox 360
Xbox One
Xbox Series
Open Relationship
Completed 10 chapters in Co-op on any difficulty
30
How to unlock the Open Relationship achievement in Gears of War 2 - Definitive Guide
ZServ
TrueAchievements
TrueAchievements
If you're playing on insane, you'll probably need to co-op anyway. Otherwise, get a friend to either play with you local or online. After 10 chapters, (when text comes up on the screen saying the name of the act, then the chapter) you'll be awarded with the achievement.