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

Ninjitsu (10 points): Defeat three opponents with a direct attack.
Lofty Goal (10 points): Clear out April's Loft, losing 10 health or less, in a Local game.
Lickity Split (10 points): Clear out the Apartment and April's Loft in 2:00 minutes or less.
Fire Hazard (20 points): Rescue Master Splinter without being burned by the flamethrower.
Evade (15 points): Defeat General Traag in the Technodrome, losing 20 or less health.
Deep Freeze (15 points): Get past the freezing trap in the Technodrome, without being frozen.
Strategy (25 points): Defeat Krang's robot, losing 10 health or less.
Turtle Soup (25 points): Defeat Shredder without being turned into a regular turtle.
Superhero (15 points): Destroy all Parking Meters, Pylons, Barrels, and Speed Signs in the game.
Slice and Dice (25 points): Earn 250 points, individually, in an Xbox Live Co-Op game.
Real Ultimate Power (30 points): Defeat Shredder in an Xbox Live Co-Op game.

Additionally, there is one secret achievement:

In The Dark (0 points): Fall into a manhole five times.