Here is the full list of all 10 Kinect Sports Gems: Ski Race achievements worth 50 gamerscore.
Reach level 1 (or observe another player doing so) to gain the rank of Alpine Apprentice.
Reach level 2 (or observe another player doing so) to gain the rank of Yeti Hunter.
Reach level 3 (or observe another player doing so) to gain the rank of Slalom Samurai.
Reach level 4 (or observe another player doing so) to gain the rank of Legendary Trickster.
Reach level 5 (or observe another player doing so) to gain the rank of Avalanche Surfer.
Reach level 6 (or observe another player doing so) to gain the rank of White Wizard.
Reach level 7 (or observe another player doing so) to gain the rank of Snow Quester.
Reach level 8 (or observe another player doing so) to gain the rank of Bulletproof Rider.
Reach level 9 (or observe another player doing so) to gain the rank of Peak King.
Reach level 10 (or observe another player doing so) to gain the rank of Ski Zen Master.