Jumper Final Boss Glitch

 

When you reach the final boss. Immediately run to left or right of the stairs and stay alongside the wall. The boss will run to you. Now you must keep him within length of the stairs on either side you choose to be in. This will keep his goons from running in the room with you and the boss. They'll stay within the confines of the stairs. This will make it easier to get the "Hard Target" achievement. Just hammer away at him with combos.