From Halopedia, the Halo wiki
It's worth a sum of 25 Gamerpoints.
- Generally, this achievement is easy, but it still requires some luck. Hiding near the flag if it is at a corner will help, but watch out for a Flag Carrier's melee.
- If played on Avalanche, the easiest way is to get a Spartan Laser. So if the Flag Carrier gets on a vehicle like a Warthog, you can stop it with one shot from your laser.
- Sniper Rifle is also useful, but if the Flag Carrier is protected by a Bubble Shield or Regenerator, the sniper will be useless. If the Flag Carrier is on a vehicle, it can be tricky to execute an accurate shot.
- Another tactic on Avalanche is to get the shotgun and wait at your base for someone to take the flag. (note this requires a lot of patience)