Sinestro was a former member of the Green Lantern Corps and later he became their greatest enemy. His desire to preserve order initially saw him as one of the greatest Green Lanterns, but as the years went by, he became obsessed with preserving the order by any means necessary.
Deemed unfit to wield the power of the Green Lantern's ring by the Guardians of the Universe, Sinestro was brought down by his fellow Green Lanterns, including John Stewart, and stripped of his power ring. Swearing a blood oath of revenge and vowing to destroy the Green Lantern Corps, Sinestro began hunting Green Lanterns and collecting their rings. Sinestro has the same powers and abilities as members of the Green Lantern Corps thanks to his yellow power ring. With his ring, he can fly, travel through space, project energy, use a force field, and generate yellow energy constructs.