Green Lantern (1963) #7
First appearance and origin of Sinestro. "The Day 100,000 People Vanished" is drawn by Gil Kane. Our strange tale begins with all 100,000 residents of the West Coast town of Valdale vanishing from the face of the Earth. When Green Lantern investigates, he realizes the townsfolk disappeared at exactly the moment he was to be in town to dedicate a new orphanage. Kept from his appointment by a prior case, GL has little time to puzzle over this fantastic occurrence. Soon his astral self is drawn to Oa, where the legendary Guardians relay to him the cause for Valdale's strange plight–a renegade Green Lantern named Sinestro.
Banished to the anti-universe planet of Qward for daring to use his position as the Green Lantern to set himself up as a dictator on his home planet, Sinestro has plotted with the Weapons Makers to wreak revenge on the Guardians and their Green Lantern Corps, starting with Hal Jordan. Using a device called the Viso-Teleporter, Sinestro can kidnap anyone on Earth within its visual range but missed GL on his first try. Returning to his body (this time with conscious knowledge of the Guardians' existence), GL devises a trap–turning each resident of Coast City invisible–with only himself vulnerable to Sinestro's device. Drawn by its power to Qward, GL engages in a deadly duel with his malevolent counterpart–the first of many, many battles in a lifelong feud. Also, don't miss the back up tale: "Wings of Destiny."