Oleg Stark was the main antagonist of the Grimm episode "Game Ogre."
Stark was hired as a contact killer, but after his employer refused to pay him in gold, Stark abducted their family, keeping them hostage for two days. His employer stole his gold, and when Stark tried to sue him for thievery, he lost the case because Hank had "misplaced" some evidence.
In 2012, Stark broke out of prison by beating two guards into a comer and went on a rampage looking for revenge, as the Siegbarste race is renowned for taking grudges to the grave. He first attacked the judge who prosecuted him, murdering him in an unspeakably brutal method of forcing his gavel down his throat. Next, he murdered the man who gave the judge the verdict and his defense attorney.
Finally, Stark began searching for Hank to end his vendetta. He attacked an elderly man and blew up his car near Hank's old residence, unaware Hank had moved. Still getting nowhere, he broke into Nick's home. Nick tried to fight back, but Stark's superior strength and durability proved too much. He tried to beat Hank's location out of Nick, before realizing Nick was a Grimm and thus could see his monstrous appearance. This caused Stark to turn more violent. At that moment, Nick's girlfriend, Juliette, returned. Panicking, she tossed a pot full of boiling water over Stark, distracting him long enough for Nick to reach his gun. After firing at Stark three times, Stark retreated but had to Nick to be hospitalized for his injuries.
Meeting up with Monroe, Nick remembered that one of his ancestors' diaries had described a weapon built to combat a Siegbarste A three barrel elephant gun, with bullets coated in a special poison could kill even Stark. With Nick incapacitated Monroe would have to get the gun and stop Stark.
Meanwhile, having finally driven him out, Stark met Hank. Hank tried to fight, but Stark easily threw him to the ground, and he lifted a giant stone slab, intending to crush Hank. However, Monroe had collected the rifle and shot Stark in the back while hiding in the shadows. The gun and poison proved too much even for the giant ogre, and he was killed.