Green Lantern Vol 3 #50

Rough Grade: 9.4

Emerald Twilight Part 3

1ST APPEARANCE OF HAL JORDAN AS PARALLAX AND KYLE RAYNER AS GREEN LANTERN

Hal Jordan battles Sinestro, a former Green Lantern, on the planet Oa. The Guardians of the Universe had previously imprisoned Sinestro in the Main Power Battery, but released him to stop Jordan. Hal kills Sinestro and Kilowog, another Green Lantern. 
After the death of the other Guardians, the remaining energy is given to Ganthet, who becomes the sole Guardian. Hal then absorbs all the energy from the Central Power Battery, which gives him a new costume and the name Parallax. 
Hal Jordan became Parallax after Mongul destroyed his hometown of Coast City. Jordan descended into madness and destroyed the Green Lantern Corps, killing his friend Kilowog and all of the Guardians, except for Ganthet.