"Sinestro was born on the planet Korugar in space sector 1417. His dedication to preserving order originally manifested in his previous career, an anthropologist specializing in reconstructions of ruins of long-dead civilizations. One day while he was on one such site, a Green Lantern named Prohl Gosgotha crashlanded into the site, injured and apparently dying. He quickly gave his ring to Sinestro, just in time for Sinestro, who barely even understood what the ring could do, to defend himself from the Lantern's pursuer: a Weaponer of Qward. However, Sinestro had to destroy the very ruins he had spent loving care restoring in order to crush the Qwardian. Afterward, Gosgotha turned out to still be alive and asked for his ring back to keep him alive long enough to get help. Sinestro, knowing this would mean not being a Green Lantern himself, instead allowed him to die and took over his post, the Guardians unaware of his actions. In Green Lantern #45 we see for the first time his wife in a flashback and that it is, in fact, the sister of Abin Sur.
His desire for order did well by him in the Corps and initially led him to be considered one of the greatest Green Lanterns. As the years passed, he became more and more fixated upon not simply protecting his sector, but on preserving order in the society of his home planet no matter the cost. Eventually he concluded that the best way to accomplish this was to conquer Korugar and rule the planet as a dictator.
When Hal Jordan joined the Green Lantern Corps, Sinestro was assigned to be his instructor. Jordan was horrified at his new mentor's totalitarian methods, though Sinestro maintained that his iron-fisted rule was necessary to protect his people from alien forces. During his training, Jordan helped Sinestro repel an attempted invasion of Korugar by the alien warlords known as the Khunds. When Jordan called for help from the other Green Lanterns, Sinestro's dictatorship was exposed and he was forced to appear before the Guardians for punishment. Katma Tui, the leader of a Korugarian resistance movement who felt that Sinestro's "protection" kept her people from growing as a society through contact with other alien races, was recruited as his replacement in the Corps. Though Katma Tui eventually grew into one of the most respected Green Lanterns, she and the rest of Korugar initially resisted her appointment to the Corps. Due to Sinestro's actions, Korugar had come to consider the symbol of the Green Lantern Corps an emblem of terror and oppression." [from: wiki] He is also revealed to be the father of Soranik Natu, a Green Lantern who currently holds his old post within the Corps.
Green Lantern (vol. 2) #7 (July–August 1961). Sinestro's first appearance in the green lantern comic. He is also a part of the upcoming Green Lantern movie.
Sinestro with apprentice Hal Jordan in the animated movie Green Lantern: First Flight.
Here is DCUC’s Sinestro in his Green Lantern Uniform.
Close up with one of the most famous comic villain.