While playing as Venom in Free Roam mode, destroy something to enter a mini-game where the police and military will try to kill Venom. Then, pause the game and choose the "Unlockables" selection. A message will appear saying you will exit your mission if you continue. Confirm to exit the mission, then exit back out of the "Unlockables" screen and return to the game. Venom can now destory anything without the police or military appearing and attacking him.