Commissioner Gillian B. Loeb is a corrupt GCPD commissioner.
Gillain makes his first appearance in Frank Miller's Batman: Year One as the corrupt Gotham City Police Commissioner who hired Lieutenant James Gordon. Loeb surprisingly liked Batman's first appearance, calling off any units sent by Gordon to capture him, as the Dark Knight gave the people "false" hope. Loeb liked the Caped Crusader until he crashed a party Loeb was attending and tied up Loeb's favourite criminal, Falcone.
The enraged Loeb turned armies of officers against the Bat, but his unsuccessful arrestings resulted in several failed attempts to bring the vigilante to "justice". Later, Batman, Harvey Dent, and Gordon revealed to the public of Loeb's workings with Falcone's mob, so the corrupt officer was replaced.
In Batman: Dark Victory, Loeb sided with the Hangman, where Loeb was eventually killed by his own partner.
In the New 52 continuity, during the Batman: Zero Year (the New 52 remake of Batman: Year One) Loeb did start as corrupt, but after the event, he chose to resign after learning that Black Mask had killed some his men because he felt responsible for allowing his department to become too corrupt.
Batman: Arkham OriginsLoeb appears in the Batman: Arkham Asylum prequel, Batman: Arkham Origins, as, yet again, a corrupt police officer in charge of the GCPD. However, he was betrayed by The Joker (who was impersonating Black Mask) where Loeb was thrown into Blackgate Prison's execution chamber (which was meant for the Calendar Man) and was killed via gas before a young Batman could help.
Later in the game under the influence of Copperhead's neurotoxin, Batman hallucinates Loeb chastising him for not helpping him, representing Batman's guilt over not being able to save the corrupt commissioner before he was murdered.
Gilliam Loeb appears in the TV Series Gotham and as a supporting antagonist in the first season.