Here is the full list of all 17 MOBILE SUIT GUNDAM BATTLE OPERATION 2 achievements.
Rank up to B+ Rating.
Rank up to Rating B.
Get promoted to Master Sergeant.
Rank up to Rating B-.
Rank up to C+ Rating.
Rank up to Rating C.
Rank up to Rating C-.
Get promoted to Sergeant.
Rank up to D+ Rating.
Get promoted to Corporal.
Rank up to Rating D.
Get promoted to Lance Corporal.
Sortie into battle 10 times.
Get promoted to Private First Class.
Defeat a rival.
Complete "Exploring the base camp" training.
Acquire 10 MS.