You'll have to complete appropriate achievement to get the allotted gamerscore.
Bounty Hunter (100) - Bring to justice all of Rivellon's most wanted criminals.
Pillar of Strength (100) - Upgrade all your Battle Tower platforms to their maximal potential.
Dragon Knight (99) - Finish the game.
Castle Crasher (80) - You have destroyed all of Damian's Flying Fortresses.
Divinity (40) - Reach an epic level.
Bunny Bagger (30) - You have killed the Killer Bunny.
Adrift (30) - You have found Michael's raft.
Family Fortune (30) - You have read the mind of the three Gremory siblings.
Chicken Out (25) - Kill Casper.
The Sigil, the Seal (25) - You have found the seal that will open the gate to the Hall of Echoes.
She Never Saw It Coming (25) - Scare away the fortune teller.
Past the Gates (25) - You have reached the Hall of Echoes.
The Dragon Roars (25) - You have destroyed Damian's armada and successfully protected your Battle Tower.
All Aboard! (25) - You finished Farglow. Happy hunting!
Path of the Pious (25) - You have gained entry to the Maxos Temple.
Lovis Lore-Master (25) - You correctly answered all of the questions about Lord Lovis.
Dim Lights, Dark City (25) - You have discovered Aleroth.
Shielded (25) - You have obtained the shield that will protect you in the Hall of Echoes.
Spell-Struck (25) - You have found the spell that will reveal the Hall of Echoes.
Dragon Ho! (25) - You have found a true Dragon: the Patriarch.
Cave In (25) - You have found Adah and Mahalath's secret cave.
The Great Escape (20) - You have made it out of the Maxos Temple.
The Maxos Baedeker (20) - You have found the book that will lead you to the Hall of Echoes.
Saint or Satan (20) - You have shown you are either utterly good or evil in Bellegar's cave.
Hold the Key (15) - You have obtained the key to the Maxos Temple.
The Feral Fjords (10) - You have discovered the Orobas Fjords.
The Damned One (10) - You met Damian.
Turn a Blind Eye (10) - Cure blindness.
A Dragon Stone's Throw Away (5) - Use the Dragon Stone.
Mirror, Mirror (5) - Make use of an illusionist's services.
Shape of the Dragon (5) - Morph into a Dragon.
Shop Till You Drop (5) - Trade with someone.
Mater Studiorum (5) - Make use of your skills trainer.
Master Brewer (5) - Create a Potion.
Enchanté (5) - Enchant an item.
Prince Charming (5) - Charm an item.
Off the Leash (5) - Summon your creature.
Gaining Power (5) - Level up once.
Peeping Tom (5) - Read someone's mind.
On the Run (5) - Send one of your runners on a mission.
You're Going to Die, Charlie (1) - You have killed Charlie the goblin.