Indestructible Creatures of NIGHTMARE ISLAND!
Andrew Helm, the last survivor of a peaceful society that was destroyed by superstitious outsiders has invested all his time to creating the Corti-Concious Machine, a device that channels the goodness of histories greatest humanitarians and imposes it on the entire population of the Earth.
This happens as the Flash is battling Mirror Master and the Shark, and Batman is battling the Penguin and Captain Cold. During both heroes fights, they are shocked to find their opponents suddenly go from being evil to being good. Traveling to JLA headquarters, the JLA members are shocked to learn that all over the world every human being is ending conflict and turning to peace.
Helm's achieved world peace is only short lived however when his machine malfunctions and suddenly the world erupts into total chaos and violence. Having been out of his physical body too long, Helm finds that he is trapped and cannot shut down the device. However, he manages to get the Justice League to go to his island base and fight off the nightmare generated devices in order to shut the machine down. With the device deactivated and the planet restored to relative peace, Green Lantern seals the island in a dome and the JLA return home wondering who built the device to begin with.