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