How To Unlock: Capture 50 flags from the enemy camp. (Multiplayer)
Simply capture a total of 50 flags in Capture the Flag games. This has of course to be done in a multiplayer game. This trophy can be easily boosted on your own. When you enter the multiplayer menu, you should get the option to enter via either an Online or LAN network. Set up a LAN Capture the Flag match, and set the win condition to be 1st to reach 50 flag captures. The trophy should pop at the end of the match. These games will not count towards your overall online wins, but at least you can concentrate on getting kills from then on.
Multiplayer > Lan > Create a Game
Set the Minimum Players setting to 1, the Reward Limit to 50 and the time to 1:30:00