The Anti-Green Lantern Corps was a group of villains from DC comics that were, unsurprisingly, enemies of Green Lantern - appearing in 1982, the organization are no longer part of DC Comics official canon, but can be considered one of many concepts in comic books that are currently in "limbo" until future writers take interest in reviving them.
The Anti-Green Lantern Corps are artificial beings who were created when the Weaponers of Qward completed a century-long task of forming a mockery of the Green Lantern Corps, empowered by their own rings. However, these anti-rings were very volatile and thus the Anti-Green Lantern Corps had very short life spans as a result.
Made en mass the Anti-Green Lantern Corp grew to at least 2000 members before they clashed with the Green Lantern Corps proper - the Weaponers of Qward had hoped to capture Hal Jordan and use his ring to further empower the group but he successfully overpowered them.
After a battle involving 200 Green Lanterns and 2000 Anti-Green Lantern Corps Arisia, Hal Jordan and Katma Tui teamed up to successfully shatter the Central Power Battery of the Anti-Green Lantern Corps, which caused their rings to become useless and forced the group to disperse.
They have not been seen since this incident or even mentioned again in-universe (though the story is often reprinted, as recently as 2006).