Question: how to unlock all characters in resident evil 6 mercenaries?
Answer: Helena (Mercs) - Score a B Rank or Higher in Urban Chaos.
Piers (Mercs) - Score a B Rank or Higher in Steel Beast.
Sherry (Mercs) - Score a B Rank or Higher in Mining the Depths.
Ada (Mercs) - Complete Ada's Campaign.
Carla (Mercs) - Unlock all other characters and their costumes.