The Green Lantern Corps represent the greatest peace-keeping force in the DC universe. Created by the Guardians of the Universe, they channel the power of will through their rings, which allow them to form hard light constructs. As great as these heroes are at battling evil throughout the universe, they can always use an upgrade that can help them in their mission, and some of these come from villains.
Source:https://www.cbr.com/green-lantern-villain-upgrades-ranked/