The lights are on
This is a supermariobros wii page. But i dont understand why that dont have one for the supermariogalaxy 1 & 2. Anyways this is how to defeat bowser in the last boss level.
Position Mario in front of Bowser, being sure to avoid the spikes, and perform a spin attack by shaking the wii remote. This will temporarily knock off the boulder protecting Bowser.
Run in the opposite direction of Bowser to meet up with him on the other side of the rotating sphere and perform a second spin attack. This will send Bowser spinning off in the opposite direction. Spin attack Bowser a final time to advance to the second part of the battle.
Stand behind the green "Bulb" plants and spin attack them once Bowser is near. If you hit Bowser with the bulb plants, his shell will fall off and he is susceptible to the spin attack. Remove his shell and spin attack him twice to move on to the final phase of the battle.
Lure Bowser to smash through any of the blue domes on the final sphere. This will catch his tail on fire. Run around the sphere in the opposite direction of Bowser and spin attack his tail.
Spin attack Bowser as he lies on his back, then repeat the sequence to defeat him entirely.