Sinestrash is a combo of Sinestro and Whiplash. He has had many countless battles with Iron Lantern.
He was a former Iron Lantern, who was jealous of Hal Stark, and went to Mandarallax for the power to destroy Hal Stark. Mandarallax gave him a yellow ring that can create an electric whip powered by the fear he strikes into the heart of his victims. Now he constantly battles Hal Stark and the Iron Lanterns as... Sinestrash!