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

Blue Lagoon Clean Sweep (20 points): Complete all Sector Challenges in Blue Lagoon.
Needle Hills Clean Sweep (20 points): Complete all Sector Challenges in Needle Hills.
FEBA Clean Sweep (20 points): Complete all Sector Challenges in the FEBA.
Grave's Bog Clean Sweep (20 points): Complete all Sector Challenges in Grave's Bog.
Hanging Gardens Clean Sweep (20 points): Complete all Sector Challenges in the Hanging Gardens.
Plains of Goliath Clean Sweep (20 points): Complete all Sector Challenges in Plains of Goliath.
Iknimaya Clean Sweep (20 points): Complete all Sector Challenges in Iknimaya.
Swotulu Clean Sweep (20 points): Complete all Sector Challenges in the Swotulu.
Va'erä Ramunong Clean Sweep (20 points): Complete all Sector Challenges in Va'erä Ramunong.
Kxanìa Taw Clean Sweep (20 points): Complete all Sector Challenges in Kxanìa Taw.
Torukä Na'rìng Clean Sweep (20 points): Complete all Sector Challenges in Torukä Na'rìng.
Clean Sweep of Pandora (75 points): Complete every Sector Challenge in the game.
Turn the Tide (25 points): Claim 50% of all territories.
Digital Bookworm (20 points): Unlock 20 Pandorapedia articles.
Weapon of Choice (20 points): Kill 100 enemies using the dual wasps or the bow.
Jack of All Skills (30 points): Use every Rank 4 skill 20 times.
A God is Upon Us (20 points): Get 10 kills in a row without dying.
Bring On All Comers! (20 points): Complete 150 Multiplayer games.
The Enemy's Bane (20 points): Finish a Team Deathmatch with the most kills of either team.
Flawless Victory (20 points): Win 3-0 in 'Capture the Flag'.
Destructive Preservation (20 points): As an RDA grunt, reach the end of the timer with 3 intact missiles.
Pandora's Protector (20 points): As a Na'vi warrior, reach the end of the timer with 3 intact crystals.
The Conqueror (20 points): Win 5 'Capture and Hold' matches.
Central Focus (20 points): Win 5 'King of the Hill' matches.

Additionally, there are fifteen secret achievements:

Orientation Day Graduate (10 points): Complete your first Hell's Gate visit.
War's Begun (20 points): Complete Blue Lagoon
The First Harmonic (20 points): Score your first harmonic in Needle Hills.
Harmonic in the FEBA (20 points): Score a harmonic from the FEBA.
Ryder Owns Goliath (20 points): Complete the Plains of Goliath.
Song of Kxania Taw (20 points): Secure the song in Kxanìa Taw.
Song of Vaera Ramuong (20 points): Secure the song in Va'erä Ramunong.
Song of Toruka Naring (20 points): Secure the song in Torukä Na'rìng.
The First Song (20 points): Secure the song in the Swotulu.
Did We Win? (20 points): Survive the RDA attack in Iknimaya.
Grave's Bog Harmonic (20 points): Score the Harmonic in Grave's Bog
Two Traitor Cleanup! (20 points): Kill Langley and Epstein in the Hanging Garden.
Hasta la vista, Harper (20 points): Kill Harper in Mist Ridge.
More Tawtute Will Come (100 points): Finish the game on the Na'vi side.
The Battle's Won (100 points): Finish the game on the RDA side.