ARCADE Player Achievement
Reach level 20 in the Arcade (Arcade only).
After every Arcade match, you will earn a good amount of XP. Typically, after a game of Deathmatch or Team Deatchmatch, you will earn half of a level and winning will net you slightly more. Playing on a custom map may give a 20% XP bonus if you remain undetected or clear the Outpost without raising any alarms; however, Deathmatch and Team Deathmatch is the quickest way to get this achievement done.