Larfleeze, Agent Orange, the wielder of the Orange light grows his lantern corps by consuming an individual and then replicating them using his ring. See how his other “constructs” kill and consume Green Lantern Gretti, then turns him into an Orange Lantern. I think this makes Larfleeze a candidate of most powerful in the universe if he manages to consume enough powerful people.
From – Green Lantern Vol. 4 #40