I need help getting some achievements. If you want to help tell me.
My gamertag is CoDeX1993
Code:
One-Night Stand 
Complete 1 chapter in co-op on any difficulty (Marcus or Dom) 10



Open Relationship 
Complete 10 chapters in co-op on any difficulty (Marcus or Dom) 30



Friends with Benefits  
Complete all acts in co-op on any difficulty (Marcus or Dom) 50
Maybe the Horde achievements too. I have all maps.