The Winterfest Add-on for Steep has 6 achievements worth 100 gamerscore.
Stay on the Sled without falling for 30 seconds (Winterfest DLC required)
Defeat "The Beast" during Winterfest
Defeat "The Dragon" during Winterfest
Defeat "The Fratelli Twins" during Winterfest
Defeat "The Super Savoyard" during Winterfest
Defeat "Lincoln Black" during Winterfest