Justice League of America, Vol. 1

After helping the League defeat the aliens, Two-Face is being returned to Arkham by Green Lantern until they are attacked by a Qwardian Weaponer who knocks the Lantern unconscious and frees Two-Face. Taken to the Weaponer's leader, Two-Face agrees to help them and watches as the Weaponers destroy Niagara Falls.Superman and Aquaman return to the Falls to prevent the flood and find Two-Face waiting for them. He surreptitiously places power blast devices to both of the Leaguers who then find and interrogate one of the Qwardians. Learning of their plans, they summon the rest of the League and split up to fight the Qwardians across the Earth.Each of the League members are surprised at the increase in their strength until the Atom works out what is happening - the Qwardians aren't siphoning energy from the alien's universe but the League are. Realising this, the League allow themselves to be defeated, sending the energy back to its home universe. Removing the power blast devices, they then defeat the Qwardians and return Two-Face to Arkham Asylum.