The pale orc pursued by Thorin Oakenshield in The Hobbit is Azog. In Peter Jackson’s Hobbit film trilogy, Azog is the primary orc antagonist and Thorin’s personal arch-enemy, driven by a longstanding feud between their families.
Azog leads attacks against Thorin and the Company of Dwarves, including the pursuit that begins before the events of An Unexpected Journey. His distinctive pale appearance earned him the nickname “Azog the Defiler,” and he is portrayed as a powerful, unusually large Orc commander.
This version of Azog differs significantly from Tolkien’s book. In The Hobbit novel, Azog is already dead before Bilbo’s adventure begins: he killed King Thrór but was later slain by Dáin Ironfoot at the Battle of Azanulbizar. The films expand him into a continuing villain and give him a major role in the story.
A common mix-up is Bolg, Azog’s son, who commands the Orc forces during the Battle of the Five Armies. Gollum is associated with the One Ring, while Smaug is the dragon occupying Erebor.