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

The Battlemaster (20 points): Do you have a taste for blood? Participate in battles and find out.
The Rules of Consecution (30 points): Are you keeping an eye on the chain count? Try to get as high a number as possible.
Death and Destruction (30 points): Do you want your party members to grow stronger? Try defeating lots of monsters.
Unleashing Secret Powers (10 points): Are you putting Timeshift to good use? Try using it as often as possible.
Timing is Everything (10 points): How is your hand-eye coordination? Try using Critical Triggers whenever possible.
The Guildmaster's Faith (10 points): Have you accepted the guild masters' challenges? Try finishing lots of guild tasks.
March of the Soldiers (10 points): Do you want a bigger party? Recruit some soldiers at a guild.
The Heir of Ultimate Fate (30 points): Have you been creating items? Try creating a certain one...
The Ravenous Hunter (30 points): How is Mr. Diggs? Try harvesting a certain item...
Guru of the Mystic (30 points): Do you like collecting items? Try obtaining a certain one...
Monster Dismantler (20 points): Are you collecting components? Try taking apart lots of monsters.
Reduce, Reuse, Recycle (20 points): Do you recycle? Try taking apart lots of equipment.
The Lone Fighter (30 points): Do you want a challenge? Defeat the monster that appears from a certain quest.
The Dragonslayer (40 points): For a bigger challenge, defeat the monster that appears from a certain quest.
The Great Soldier (40 points): For a huge challenge, defeat the monster that appears from a certain guild task.
Hero of the Dawn (50 points): For a great challenge, defeat the monster that appears from a certain guild task.
The Godslayer (140 points): For the biggest challenge of them all, defeat the monster they call The Fallen.

Additionally, there are five secret achievements, two of which are currently unknown:

The Bloodhunter (30 points): You have defeated over 30 monsters in one battle. You must have lots of rare items!
Living Rich (10 points): You have obtained over 200,000G. Are you taking your friends out for nice meals?
Lost Words of the Gods (10 points): You have spent over 100,000G. Would you like some investment advice?
Secret achievement (200 points): Unknown.
Secret achievement (200 points): Unknown.