Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Instant Gratification (20 points): Complete all Instant Action maps on any difficulty in any order.
Glutton for Punishment (55 points): Complete all Instant Action maps on Extreme difficulty in any order.
Entering Desolation (30 points): Complete the Extraction Point campaign through "Holiday".
Confronting the Leviathans (30 points): Complete the Extraction Point campaign through "The L".
Living in Fear (60 points): Complete the Extraction Point campaign.
Mastery of Fear (75 points): Complete the Extraction Point campaign on Extreme.
Achievement Boost (40 points): Find all the health and slo-mo boosters in the Extraction Point campaign.
No Batteries (15 points): Complete the Extraction Point campaign without letting the flashlight run down.
Fear My Wrath (55 points): Kill every enemy in the Extraction Point campaign.
Take a Message (15 points): Answered all the phones in the Extraction Point campaign.
Laser Showoff (15 points): Kill 30 enemies with the Type-12 Laser Carbine.
Minigun Marauder (15 points): Kill 30 enemies with the TG-2A Minigun.
Control Freak (15 points): Capture 25 control points in ranked Control matches.
Conquering Hero (15 points): Capture 25 control points in ranked Conquer All matches.
Cycle of F.E.A.R. (35 points): Win a ranked multiplayer game on all maps (gametype not important).
Fear the Reaper (10 points): Kill 3 players while SloMo is active in a ranked SloMo multiplayer match.
Arrival At the Scene (20 points): Complete the Perseus Mandate campaign through "Underneath".
Understanding the Enemy (20 points): Complete the Perseus Mandate campaign through "Disturbance".
Beginning of the End (20 points): Complete the Perseus Mandate campaign through "The Plaza Chase".
Former Foes (20 points): Complete the Perseus Mandate campaign through "Basecamp".
A Darker Place (20 points): Complete the Perseus Mandate campaign through "Labyrinth".
An End to FEAR (35 points): Complete the Perseus Mandate campaign.
Nothing to FEAR (50 points): Complete the Perseus Mandate campaign on Extreme difficulty.
More Assault Than Recon (40 points): Kill every enemy in the Perseus Mandate campaign.
High-Tech Hitman (10 points): Kill 20 enemies with the LP4 Lightning Arc Weapon in the Perseus Mandate Campaign.
An Advanced Arsenal (10 points): Kill 30 enemies with the VES Advanced Rifle the Perseus Mandate Campaign.
The Bouncing Boom (10 points): Kill 20 enemies with the K3-BT Grenade Launcher in the Perseus Mandate Campaign.
Arms Master (10 points): Kill enemies with every weapon at least once in the Perseus Mandate campaign.
Detective (10 points): Find all phone messages and laptops in the Perseus Mandate campaign.
You Like the Juice (10 points): Find every booster in the Perseus Mandate campaign.
Mastered Your FEAR (50 points): Complete the Perseus Mandate campaign without dying.
Action Initiate (25 points): Complete any Instant Action map.
Action Veteran (25 points): Complete any Instant Action map on Extreme difficulty.
Camping the Goods (25 points): Obtain 150 Health and 100 Armor in a multiplayer game.
Test Drive the New Toys (25 points): Kill players in ranked multiplayer with the VES, K3-BT, LP4, TG-2A, and Type-12.
A Player to FEAR (25 points): Kill 10 players without dying in multiplayer.

Additionally, there are five secret achievements:

First Encounter (10 points): Defeat the first Nightcrawler Elite.
A Friend In Need (10 points): Tried to save Chen.
While You're Down There (10 points): Kill 10 critters such as rats and crows in the Perseus Mandate campaign.
Cutting Off Heads (10 points): Defeated the Nightcrawler commander.
You Must Be on the Team (5 points): Watch the Perseus Mandate campaign entire credits.