Sinestro History
[CBR]: Superman has Lex Luthor. Batman has the Joker. Hal Jordan of the Green Lantern Corps has Sinestro -- but not just Hal Jordan; the entire Green Lantern Corps fears the renegade Green Lantern and his yellow power ring. This June, Geoff Johns and Ethan Van Sciver will bring us DC Comics' "Sinestro Corps Special," featuring this unique villain and his answer to the Green Lantern Corps that he betrayed and has ultimately vowed to destroy....Sinestro makes his first appearance in "Green Lantern" Vol.2 #7. Sinestro's homeworld is the planet Korugar. He is selected as Green Lantern of space sector 1417 by the Guardians of the Universe. Growing bored with his responsibilities, Sinestro uses his power ring to create a "sumptuous headquarters" where he dispenses "justice" from a throne to the supplicants that appear before him. When a Korugarian citizen calls Sinestro "power mad," the Green Lantern kills the man and makes himself a dictator. After some time, the Guardians look in on Sinestro and, seeing that he has become corrupt, recall him to Oa, the Guardians' homeworld. There, the Guardians strip Sinestro of his ring and insignia, and banish him to the anti-matter universe of Qward...
Read this comprehensive, fascinating round-up of old Yellow-Ring's history.