Sinestro currently operates a ring running on the yellow spectrum power of Fear, in which inexperienced Green Lanterns are weak to. Sinestro is a cunning, ruthless villain, although he will ally himself with the Green Lanterns if it benefits himself or existence in general. Sinestro believes himself actually fighting for the greater good, and is always quick to point out his perceived inaccuracies and hypocrisy that the "good guys" exhibit.
Sinestro's best friend was Abin Sur, Hal Jordan's predecessor. After Sur's death, Sinestro was paramount in Jordan's training, although he was convinced that the human would never be able to equate his fallen comrade's legacy. The two have a grudging respect for one another that continues even when they're on opposite sides of the war, though it rarely surfaces.
During the Blackest Night, in which many heroes and villains became reanimated zombie "Black Lanterns", Sinestro surprised everyone by becoming the first ever White Lantern. Although this didn't last, it was still enough to shock everyone other than himself.
Just prior to DC's "new 52" reboot, Sinestro yet again became a Green Lantern.