What Happened To All The Lantern Corps?

The only section of the Corps named after someone and not something, the Sinestro Corps are named after their erstwhile villainous leader and former Green Lantern, Thaal Sinestro.

After his obsessive prevention of any crime in his sector makes him quasi-accidentally become a dictator, the Green Lantern Sinestro was banished by the Guardians into the Antimatter Universe, which he returns from with a mysterious yellow ring - the first Yellow Power Ring - and a profound hatred for the Green Lanterns.

Sinestro would expand his Corps by inviting those capable of generating mass fear into his team, extending it into a legitimate threat against the Green Lanterns.

While there would be many challenges to the villain's leadership - such as Mongol's coup after the Sinestro Corps War - these attempts would all eventually fail, leaving Sinestro in charge once more. In a weird way, this is likely for the best, as Sinestro is willing to put aside his hatred of the Green Lanterns during Blackest Night to take down Nekron, proving that the Sinestro Corps aren't always entirely evil.