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

Stalker (15 points): Complete the stealth tutorial.
Burglar (15 points): Complete the lock picking tutorial.
Monkey (15 points): First time climbing completed!
Fighter (15 points): Complete the fighting tutorial.
Ninja (15 points): Complete chapter one without getting spotted.
Locksmith (15 points): Successfully lock pick or unscrew five doors or grates without being spotted.
Pugilist (15 points): Don't get knocked out in five consecutive fights.
First Blood (15 points): Beat your first opponent in underground fights.
Unbruised (15 points): Win a match flawlessly in underground fights.
Ringer (15 points): Defeat 50 enemies in underground fights.
All Inked Up (15 points): Get tattoos for all six locations on your body.
Swole (15 points): Lift the weights for at least 10 minutes (accumulated).
Bloody Knuckles (15 points): Punch the heavy bag for at least 10 minutes (accumulated).
Doesn't Play Well with Others (90 points): Beat up more than 100 people on Shark.
Untouchable (30 points): Win a match flawlessly in underground fights on Shark.
Mogul (30 points): Earn $5000.
Indefinite Furlough (30 points): Finish the game at any difficulty.
The Great White (85 points): Finish the game on Shark.
Invisible (90 points): Complete every chapter without being seen.
Lightning Reflexes (30 points): Successfully perform 50 reversal moves in fights.
The Best Defense... (30 points): Win a fight without blocking.
Insult to Injury (30 points): Win a fight using only reversal moves and finishing moves.

Additionally, there are 23 secret achievements:

Initiation (15 points): Arrive in Fox River.
Quid Pro Quo (15 points): Complete the first quest to retrieve C-Note's drugs.
Birds of a Feather (15 points): Realize the brothers are breaking out.
Enabler (15 points): Get the PUGNAc.
In the Crazed Mind's Eye (15 points): Steal Haywire's sketches.
Built for the Rough and Tumble (15 points): Survive the riot.
Inside Job (15 points): Find out that Turk works for the Company.
Man with the Plans (15 points): Get the prison blueprints.
Matador (15 points): Beat Bellick in the underground fight.
Company Policy (15 points): Mannix arrives at Fox River.
Unfinished Business (15 points): Relentlessly pursue Mannix over the rooftops.
Everything and the Sink (15 points): Dispatch Trumpets with the sink.
Early Retirement (30 points): Terminate Mannix.
Tunnel Rat (15 points): Knock out Bellick in the sewers.
Guardian Angel (15 points): Stop Mannix from killing Linc.
Hard Boiled (15 points): Escape from the boiler room ambush.
Brutally Chained (15 points): Hang Teets with his own chain.
Shock and Awe (15 points): Jump away from the water before getting electrocuted.
Massive Overdose (15 points): Escape from the asylum after being injected with drugs.
Metal Twister (15 points): Make it out of the elevator shaft unscathed.
The Rat Hunt is On (15 points): Secure the letter of testimony.
Blood Red Tiles (15 points): Defeat the snitch in the shower room.
Guacamole with Lard (15 points): Escape Avocado's stranglehold.