Here is the full list of all 40 Metro Conflict achievements.
Add 1 friend
Create/Join a Clan
Get promoted to Staff Sergeant
Get promoted to Sergeant First Class
Get promoted to Master Sergeant
Get promoted to Second Lieutenant
Get promoted to First Lieutenant
Get promoted to Captain
Get promoted to Major
Get promoted to Lieutenant Colonel
Get promoted to Colonel
Get promoted to Brigadier General
Get promoted to Major General
Get promoted to Lieutenant General
Get promoted to General
Make 10 or more weapon purchases
Make 50 or more weapon purchases
Make 300 or more weapon purchases
Make 1000 or more weapon purchases
Accumulate 500 kills with Striker
Accumulate 500 kills with Ana
Accumulate 500 kills with Hawkeye
Accumulate 500 kills with ElTigre
Accumulate 500 kills with Chris
Accumulate 500 kills with Big Daddy
Accumulate 500 kills with Geoffrey
Accumulate 500 kills with Trish
Defend Strongpoint 50 times
Win 50 Deathmatches
Win 50 Demolition matches
Win 50 Cube Rush matches
Win 50 Extreme Deathmatches
Win 50 Survival matches
Add 5 friends
Add 10 friends
Add 30 friends
Accumulate 500 kills with Tiffany
Win 50 Escape matches
Accumulate 500 kills with Rona
Win 50 Extreme Domination matches