9. Guy Gardner - Injustice Year 2
Considering that the entire mission statement of the original Injustice tie-in comic was to explain why the rest of the DC universe outside of the game's original character roster was absent from the proceedings of the game's story, it stands to reason that there are some rather... excessive deaths, sprinkled throughout this slaughterhouse of a series.
In Year 2, the Green Lantern Corps decide that they've had quite enough of Superman's shenanigans and bring the entire corps down on his head to take him down. They even strip Hal Jordan of his powers when he sides with Superman.
However, in comes Sinestro to play to Hal's anger and ego by tricking him into thinking Guy Gardner (who was basically acting like the only adult in the room, to give you an idea of how bad things have gotten by now) had murdered his girlfriend.
Armed with a new yellow power ring, he kills Guy by brutally ripping off his ring arm with his bare hands. He then lets Guy, stripped of his powers from the loss of his ring, fall to the Earth below.