Here is the full list of all 21 Modern Combat Versus achievements.
Reach the MASTER LEAGUE
Open 200 Multiplayer Victory Crates
Reach the DIAMOND LEAGUE
Perform 5,000 kills
Win 500 matches
Reach the PLATINUM LEAGUE
Perform 2,000 kills
Win 100 matches
Reach the GOLD LEAGUE
Open 50 Multiplayer Victory Crates
Win 50 matches
Reach the SILVER LEAGUE
Perform 500 kills
Open 15 Multiplayer Victory Crates
Create or join a Clan
Win 10 matches
Perform 100 kills
Reach the BRONZE LEAGUE
Open 5 Multiplayer Victory Crates
Win 3 matches
Perform 10 kills