From the Marvel/DC Rise of the White Lantern Crossover.
Mr. Green is a mysterious unnamed agent of Norman Osborne who is tasked with stealing the Green Ring from Jeffrey Himes (with the ultimate goal of stealing every ring to empower the Orange-corrupted Norman Osborne even further.) After being confronted by Jeffrey Himes, Mr. Green uses his superior fighting skills to easily defeat the fledgling super-hero. However, in an unexpected move, Mr. Green tells the kid he has "heart" and returns the stolen ring. Jeffrey is shocked to discover the real identity of Mr. Green, and let's him escape before rejoining the battle against the black lanterns.
Mr. Green's real idenity is known only to Norman Osborne and Jeffrey Himes. Though Norman does imply that he may have worked for H.A.M.M.E.R. and that he was "well piad for this assignment."

Mr. Green is made from a DCUC Guy Gardner with vest removed. The head is a scultped over Sinestro, and the entire figure was given a reapint.