Firefight: Lost Platoon
From Halopedia, the Halo wiki
Firefight: Lost Platoon is an achievement in Halo 3: ODST. It is awarded for scoring over 200,000 points during a match of Firefight on the map Lost Platoon. It is worth 10 Gamerpoints.[1]
This is probably the easiest Firefight achievement, as all you have to do is carjack a Chopper early in the game and score kills until you get 200,000 points. It is done best on Normal difficulty.
When doing this on single player, allow a minimum of 2 hours to reach the 200,000 points.
When playing with 2 or more players, it is best to get points on the bonus round where every skull is on. To do this, you and a friend must get a Warthog. (The bonus round only has Grunts, so the Tilt Skull has no effect.) The Driver can splater as many as he can while the chain gun can get even more kills. Thus, giving you extra lives and points.
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