To fight Ermac in the game you need the swing and wall run ability. simply go to the warrior shrine then use the wall run ability on the wall to your left. Then use the swing ability and swing across the poles then interact with the shrine and it will open the doors. Go across the bridge and u will find statue of the greatest fighters. Interact with the last statue on the left about three to four times and it will eventually shake and crack open. then You will begin to fight Ermac who is very hard because he throws you around the whole shrine