Let the Scorpion King to charge the pillars and hit his tail each time. Next, let him charge you again and attack from behind. Stand still until he gets mad and attacks with his super-slash. Run around behind him and hit his tail. When he drops, hit him in the torso. Repeat this process until he climbs the pillars again. He will attack again. Let him charge and attack from behind again. Wait as before, but longer. He will try to grab you. Move out of the way at the correct moment. He will get stuck. Hit his tail again, and then his torso. Repeat this until he climbs back up the pillars. Jonathan or Meela will bring the Spear of Osiris down and fail at trying to spear the Scorpion. Use the same tactic to hit his tail while he is stunned then get the spear and attack him.