Capture 100 flags. The quickest way to get this achievement, is to set up a match with the following settings:
Mode: Capture the Flag
Map: Old Town
Bots: 3 (Dark Agent)
Weapons: Custom (Rocket Launchers)
Time Limit: 10
Points Limit: 10
Put all of the bots on your team, by pressing on their name. When the game begins, run through the teleport and stand to the left of your flag. A bot will grab the enemy flag and start to bring it back. Normally, he will take the path on your left. When he comes into sight, shoot him, grab the flag by running to it, then stand on your teams flag to capture it. You can get 10 captures every 6 minutes. 100 captures will take one hour. It can be a mix of online and offline.
*You must complete the match for your achievement progress to register.