Thaal Sinestro of the planet Korugar in Sector 1417 is an intergalactic super-villain and antagonist of Green Lantern, particularly Hal Jordan. Originally known as the greatest member of the Green Lantern Corps ever to wield a ring, he trained many students including Hal Jordan. The Guardians of the Universe exiled him to the Antimatter Universe after learning he had used his power to set up a dictatorship. Having fought the Green Lanterns for many years with a yellow ring forged by the Weaponers of Qward, he established his own Sinestro Corps to spread fear throughout the universe. He has also been a member of the Injustice League, the Secret Society of Super-Villains, and a founding member of the Legion of Doom.

Reference - https://youtu.be/GlrlspPrSHc?t=213