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

Cold Blooded (10 points): Kill 25 nanite enemies that emerge when you kill host organisms.
Fully Buffed (15 points): Equip a bot with only max level parts.
Amoxicillin (15 points): Kill 1000 Bacteria.
Transmission (5 points): Enter the body.
Diving Deeper (5 points): Complete the 1st of 5 worlds.
Loco Motion (10 points): Beat a level using only movement parts.
Survivor (30 points): Beat 3 rounds in Challenge Mode.
Team Player (15 points): Kill 25 enemies while using the Co-op Link Gun.
Fullerene (25 points): Collect all 20 Bucky Balls.
Up and Atom (25 points): Amass 50,000 Atoms.
Micromania (30 points): Collect 'em all - parts, that is.

Additionally, there is one secret achievement:

Alive or Dead? (15 points): Find the source of the hostiles and destroy it.