10 Most Powerful Characters Killed By Hal Jordan's Green Lantern
8. Sinestro - Green Lantern #50
Following the destruction of his hometown, Coast City, in the Reign of the Superman arc, Hal Jordan suffered a mental breakdown and this allowed for the fear entity Parallax to possess him. This moment of vulnerability led to his rampaging throughout the galaxy before turning his sights on the Guardians of the Universe and the whole Green Lantern Corps (the former rebuked and forbade him from reconstructing his hometown).
The former Green Lantern's devastating wave was too much for his former allies to handle, and this led the Guardians to pursue drastic and decidedly unsavoury means to contain Jordan. Their solution involved resurrecting the recently deceased Sinestro, reform him, and place him on a collision course with the rampaging Hal in order to slow him down at the very least.
The former allies clashed on Oa in a spectacular brawl that boiled down to a physical fight as their Power Rings were drained. Ultimately, Hal had his opponent in a headlock and snapped his neck before continuing with his rampage.