In Single Player/Ko-Op:
Defeat the Game as Liu Kang to unlock Scorpion in Single or Ko-Op modes.
In Versus Mode Find the Red Yin Yang in The Foundry. When you first enter the Foundry you will see a long hallway infront of you. As you walk down it, you will encounter a few enemies who break out of boarded up passageways on the left and right. The final passageway on the left can be broken by throwing an enemy through it. Inside you'll find a lava pit, throw an enemy onto the Lava and use a series of Long Jump and Double Jumps to reach the platform with the Red Yin Yang that unlocks Scorpion in Versus Mode.
Spear Throw (Lev.1): [MOD] [PB]
Uppercut (Lev.1): [MOD] [BB]
Enemy Manipulation (Lev.1): [MOD] [TH] ( [JB] to release)