HOW TO UNLOCK EACH CHARACTER OF THE JUSTICE LEAGUE FOR THE ACHIEVEMENT:
Batman -- Unlocked from the start
Robin -- Unlocked from the start
Superman -- Complete level 6 (even though you can start playing as him on the city map after level 5)
Green Lantern -- Complete level 14
Cyborg -- Complete level 14
Flash -- Complete level 15
Wonder Woman -- Complete level 15
Aquaman -- Gold brick gate in northwest of middle island (requires 70 gold bricks and 125,000 Lego studs)
Hawkman -- Gold brick gate along northern edge of middle island (requires 80 gold bricks and 125,000 Lego studs)
Martian Manhunter -- Gold brick gate just north of the center of the middle island on the tall building with Luthor's presidential campaign banners (requires 175 gold bricks and 125,000 Lego studs)
ABILITIES FOR EACH CHARACTER:
Batman -- Only character that can blow up silver objects (that aren't on the ground; Penguin can destroy those) using Power Suit; only character that can walk on electric floors using Electricity Suit (Joker can activate and deactivate electric switches); only character that can stealth past cameras using Sensor Suit (any Kryptonian can use X-ray vision); can use grappling hook and Batarangs
Robin -- Only character that can wall jump, flip from flag poles sticking out of walls, climb poles and use roll pads with Acrobat Suit; only character that can suck up and spray sludge using Hazard Suit (though Aquaman can spray unlimited water); can use grappling hook and Batarangs
Superman -- Flight, super strength, laser eyes, freezing breath, weakness to Kryptonite
Green Lantern -- Flight, only character that can build with green bricks
Cyborg -- Laser eye, magnetic (just like Robin's Magnet Suit), super strength
Flash -- Fast, only character that can rebuild objects that have been destroyed by Luthor's Deconstructor Ray
Wonder Woman -- Flight, super strength, lasso can attack to objects that are pulled apart by Batman's grappling hook, can use tiara as boomerang
Martian Manhunter -- Flight, super strength, laser eyes
Aquaman -- Can spray unlimited water from trident with no need to refill, super strength, sinks in water (like Robin's Hazard Suit) and can use strength under water
Hawkman -- Flight, fights with mace
Guide made by McMurderpaws at gamefaqs.com. I thought this would be helpful to have as it is the guide I am using for the achievement.
http://www.gamefaqs.com/xbox360/655773-lego-batman-2-dc-supe...