Shadow Bowser

Shadow Bowser is Bowser's final boss in Mario & Luigi RPG 3!!!. Shadow Bowser covers the entire Mushroom Kingdom in darkness and Bowser faces him.

One of Shadow Bowser's attacks is throwing a meteor into the air and blasting it apart, causing rocks to fall out of the sky. Bowser must use his shell to avoid taking damage. However, he must punch one of the rocks to Shadow Bowser, who is charging an attack. When the rock lands in his mouth, he executes his attack, and the rock causes it to blow up in his face. Another attack has him punch Bowser repeadetly. Bowser must block a punch with his own punch. Then Shadow Bowser will jump into the air and Bowser has to hide in his shell to avoid taking damage from Shadow Bowser, who's falling out of the sky. Another attack is trapping Bowser in a cage and putting the cage in the sky. He will then charge up an energy ball. Bowser must try and destroy the cage before he gets hit by the energy ball.

At one point, Shadow Bowser will be healed and will grow giant. Bowser has to punch him in the stomach so that the bug thats making Shadow Bowser giant comes out.

Eventually, the shadow copy is defeated.