To obtain this achievement you will need to unlock the following characters:
Owlman - He will be unlocked at the end of level 13 “They Think It’s Owl Over”.
You will need to purchase him and can be done from the hub by holding

scrolling down to him, and paying the 150,000 studs for him.
Talon - to unlock him you are required to complete 2 hub challenges these are as follows:
1. Panti - Social located here:
2. Talon - t Show located here, the speech bubble next to the green tick Jonny DC:
You are required to go to the character customiser, and change into a black hood and top shown below:
Now return and finish off the mission to China town and blow up the fire work truck to unlock Talon.
You will need to purchase him and can be done from the hub by holding

scrolling down to him, and paying the 250,000 studs for him.
AchievementNow select each player within your party screen by tapping

to change second character, then pop achievement unlocked.
Congratulations!
Happy Hunting