From Halopedia, the Halo wiki
GEN2 is an achievement in Halo: Spartan Strike. It is unlocked by using every armor ability at least once. The achievement is worth 10 Gamerscore. It is represented by a circle with Spartan silhouette inside it.
Every single armor ability can be found in-game. Although the airstrike, overshield and seeker drone abilities can be purchased to unlock the achievement, these three armor abilities are also found free of charge in the final level of the game, Mission 30: Hold the Line.