The Injustice League is a group of supervillains consisting of about 7 villains (Count Vertigo, the Joker, Poison Ivy, Ultra-Humanite, Atomic Skull, Black Adam and Wotan). They are villains in the TV series Young Justice.
By using Poison Ivy's powers, they attack Metropolis with giant vines, later also targeting other cities. The Injustice League publicly takes responsibility for the attacks on major cities throughout the globe and demands a ransom of ten billion dollars. Although they do not give a time limit for the transaction, they state that the longer the UN needs, the longer they can have their fun.
After the transmission, the Justice League and the Young Justice team falsely believe the Injustice League to be The Light. The Justice League sets to fight the plants while the young team sets out to destroy the Injustice League's central control system.
During the battle with the plants, the Justice League realizes that each member of the Injustice League somehow enhanced the plants with their own individual style - for example attaching spores producing Joker Venom to them.
When the Young Justice team arrives at the League's headquarter in the Louisiana swamps, the Injustice League is alerted. Count Vertigo and Black Adam venture outside and shoot Miss Martian's bioship out of the air.
Black Adam rips the hull of the ship but is hit in the head by Superboy and falls backward. Count Vertigo continues attacking the team and Black Adam joins the fight once more. They defeat all intruders except Robin and Miss Martian who both manage to escape.
They manage to reach the control center but are there attacked by Poison Ivy and Ultra-Humanite. Robin flees from Ivy's ranks while Ultra-Humanite attempts to shoot Miss Martian out of the air. While the others battle, Joker controls the vines in the cities and Atomic Skull powers them.
When Vertigo, Black Adam, and Wotan, who is creating a cage with his mind, are delivering their captives back to base, Wotan is struck by the regenerated bioship. Unable to focus, the cage disappears and the team is free once more. The Injustice League and the Young Justice team fight once more, unaware that the fight is just a distraction for Robin and Miss Martian to blow up the main plant. Despite the destruction of the plant, the villains keep fighting.
Outmatched, the Young Justice team change to plan B. Aqualad dons the helmet of fate which transforms him into the host of Nabu, the Lord of Order. He fights Wotan while Ivy and Count Vertigo attack Miss Martian, only to be distracted and defeated by Kid Flash and Artemis. Joker attempts to stab Robin but is disarmed by a Batarang.
The entire Justice League then sweeps in and, being severely outmatched, the Injustice League surrenders. Joker, however, activates a last failsafe, exploding a bunch of Joker-venom spores. They are protected by Nabu who creates a giant energy shield around the heroes.
After the Injustice League is disbanded and humiliated, members of the Light discuss that they are now out of danger - given that the Justice League believes that the Injustice League were the society opposing them.