Get near a lava area found next to a road. Select your fists and wait for a car to drive past. Either kill the driver and exit, or do the following with the driver still inside. Use your melee attack to push the car into the lava and wait for it to explode. You can also get the car into the lava by sprinting into it or using the Stomp ability. Note: Driving the car towards the lava and bailing out will not qualify.