When the battle begins, you will be facing three Shroobs holding a large Shroob-like Bomb-omb. Attack and destroy the middle and rear Shroobs so that the front Shroob is crushed by the bomb because he cannot hold up the weight himself. The bomb will roll backwards, blowing up Commander Shroob, allowing you to attack him. The most effective attacks on him are the Ice Flower (to lower his stats, and do critical damage), Copy Flower, and Red Shell, provided you have good timing. His attack is mostly slapping Shroobs towards you;.defend with your hammers. He has a lot of HP, and the battle will last awhile because after a few turns he will summon more Shroobs with the bomb again. Repeat the first strategy to reveal Commander Shroob again, then repeat the second strategy until he is defeated. High Pow and a lot of patience is recommended.