Complete the indicated task to unlock the corresponding medal.

A Winner Is You: Complete the game.
Facerape: Get to where two persons are being trained. Get inside the building and kill the enemy in front of you but do not jump down. Wait a few seconds and the monster you fought will appear. Use your chainsaw on his face.
Pacifist: Once the Boss is defeated, let the Clown walk away.
True Face Of Evil: Once the Boss is defeated, empty your gun to throw it away. Then, just punch him in the face.