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