To easily defeat Shao Kahn in the final battle, retreat as you would normally. He will then do one of three actions; throw the spear, throw the hammer, or laugh/taunt. When he throws the hammer or taunts, teleport behind him and quickly uppercut him, then retreat again. When he throws the spear, teleport at the first possible instant and uppercut. If you are too slow, he will turn and attack. The best way to attack when he throws the spear is to teleport and jump over his head to dodge his attack, then deliver a drop kick followed immediately by the Electric Fly. Always retreat after each hit. Also, duck to dodge the spear instead of blocking, which will save you from losing health.