Super Mario Galaxy 2/Grandmaster Galaxy

The Ultimate Test
This galaxy is unlocked by getting all 120 Power Stars, and all 120 Green Stars.

Run up to the Yoshi egg and break it open. Jump on. In this area, you must cleanly cross the passage crowded with bombs, Paragoombas and Bullet Bills, by using Yoshi to swing on the flowers. Be very careful, and time your jumps to the next flower carefully; one mistimed jump could result in hitting a bomb and falling into the empty space below. Use Flutter Jumps to help float to a safe area before grabbing the next flower. Near the end of the section, Bullet Bills will join the party. Though these are easily avoided, they can catch up with you if you wait too long to make your move. At the end, you can Flutter Jump off the last flower to the Launch Star, or, failing that, jump off Yoshi and climb up the flagpole to the Launch Star.
 * First section

In this area, you must turn all of the Flipswitch panels yellow, while avoiding the Sentry Beams. Follow this path without going over a panel twice. You can either long jump if on foot or flutter kick with Yoshi to get to the last two panels, and the order of the last two panels can be switched if it's easier for you.
 * Second section

When all are turned yellow, the Launch Star will appear at the starting location.

If you still have Yoshi at this point, it's time to leave him behind. Grab the Cloud Flower, jump above the fan, create a cloud, and float up. Run right and drop down, creating another cloud when you are level with the next Cloud Flower. Float right a bit, then backflip straight up, creating a new cloud at the peak of each flip, until you are above the lasers to the right. Jump for another Cloud Flower, and create a cloud at the bottom. Float right, and use another combination of backflips and clouds to clear the lasers. Grab the next Cloud Flower, drop down, and create a cloud at the bottom. Float right, and for the last time, use backflips and clouds to clear the lasers to the right. Grab the Cloud Flower, drop down, and create another cloud when you are level with the Launch Star. Float over to it, and hop in. If you use long jumps during this section, you can have a couple helpful clouds left over when you fly to the next planet.
 * Third section

This area is made up almost entirely of those found in Flip-Swap Galaxy, i.e. spin to make the platforms switch sides. On top of this, you need to avoid several laser bots, which are very difficult to avoid, since spinning causes the platforms to flip, often unfavourably. If you have some clouds left over from the previous section, they will be useful here. To begin, clear the green vanishing platforms. Long jump to clear the greatest distance possible while (usually) avoiding beams. Only spin if necessary. After clearing the first two laser bots, Octoombas will also begin attacking (and their projectiles are repelled by spinning, making the section even harder). The better plan is to avoid them completely, only attacking if necessary. It's tough, but if you make it to the end, the Launch Star is waiting, right in front of another Octoomba.
 * Fourth section

Hop over the first long laser moving from left to right and long jump out into space all the way to the first pull star. This skips the long jump across the next, shorter one and the next two more difficult ones. Next, you need to use the Pull Stars to cross the abyss. This section requires good timing. Avoid the Paragoombas. To avoid the two lasers here, wait until they have fully retreated. The next pair of laser beams work oppositely: one moves out as the other moves in. Wait for the gap to come fully to the right before advancing. To avoid the pair of beams rotating clockwise, wait for both to point towards you, then move forward quickly. After this, a laser is blocking the path between you and the Launch Star. To get around it, follow the path of launch stars, but at the last one, release before you reach it, and you'll float off toward a coin. Get that before reaching for the last Pull Star. Drop to the platform below, and run to the Launch Star.
 * Fifth section


 * Sixth section

If you want, simply bypass the first two Hammer Bros., and run straight for the Sling Star. From there on out, though, the safest option is to defeat every Hammer Bro. you meet, starting with the one in front of you as you land. Then, travel right and defeat the Hammer Bro. here, and the one to its left. The next series of platforms rotate every few seconds, throwing you off. Use spin jumps to time your landings well. Be careful near the end, as this brings you within the next Hammer Bro.'s range. Defeat it before proceeding. Left of here is another Hammer Bro., and three Boomerang Bros. Defeat the Hammer Bro. first, otherwise it'll get in your way while dealing with the Boomerang Bros. The Boomerang Bros. are tough, not least because there are three of them. Avoid all attacks, then defeat one while avoiding the next round of attacks. Repeat until all three are gone, and Power Star number 241 will appear.

The Perfect Run
Repeats the first star only under Daredevil conditions. Some enemies are replaced by tougher ones, and there is a surprise at the end. It is unlocked by giving 9,999 star bits to Banktoad, completing the first star and retrieving the last Comet Medal on the first star.