You need to unlock:
The Riddler - Level 2 It’s Good To Be Bad
Two-Face - Level 2 It’s Good To Be BadAlso you will need to progress to a certain point in the campaign to unlock this, after you unlock the cutscenes of the Batcave it’s self
I personally got this upon completing all story missions first.Location
For this achievement to work you first need to be inside of the Batcave, in the image below is Wayne Manor on the mini map spawn or fly there whichever you prefer.
Now go into the Batcave. Achievement
Now all you need to do is hold down
and select Two-Face
to take control of your second player and repeat the above step apart from selecting The Riddler
Once you have both in a party, pop achievement unlocked.
If your not happy with the guide and want to leave bad fb please have the decency to explain why so I can update/amend to help all gamers achieve this!!!!