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

Is There a Way Out? (20 points): Complete Chapter 1.
San Francisco is safe, next! (25 points): Complete Chapter 2.
Could we Fight Something Bigger? (30 points): Complete Chapter 3.
What Alien Menace? (35 points): Complete Chapter 4.
Not a Novice Anymore (40 points): Complete the game (awarded just before credits)
Flying Fish (20 points): Perform 50 Leap Attacks with The Missing Link.
Stay Put and Watch (5 points): Watch credits until the end
Casual Collector (20 points): Collect 100,000 monster DNA particles in the game.
Never Say Enough (70 points): Collect 500,000 monster DNA particles in the game.
Full Arsenal (30 points): Buy all upgrades for all characters (Green nodes).
Two is Better than One (15 points): Buy all coop upgrades (Light Blue nodes).
Art Aficionado (30 points): Buy every concept art (Yellow nodes).
Shopping Frenzy (15 points): Buy all surprises available (Purple nodes).
That's a Blast (10 points): Have a team-mate use the Charge Blast for the first time in Coop.
Strong Attraction (10 points): Have a team-mate use the Tractor Beam for the first time in Coop.
Collateral Damage (10 points): Have a team-mate Destroy 30 EyeScouts and Helicopters in Ginormica levels in Coop.
Air Support Master (20 points): Have a team-mate Destroy 100 BHolders in The Missing Link and B.O.B. levels in Coop.
Maximum Attraction (10 points): Have a team-mate Tractor 50 enemies in The Missing Link and B.O.B. levels in Coop.
Great Tackler (15 points): Destroy 10 drones with Ginormica's dash.
Master Tackler (20 points): Destroy 25 drones with Ginormica's dash.
Get Out of the Way (10 points): Use Ginormica's chain dash for the first time.
Bring it On (10 points): Defeat a Beam Bot without getting hit.
Just Warming Up (10 points): Defeat 50 enemies with The Missing Link.
Can't Get Enough! (20 points): Defeat 100 enemies with The Missing Link.
Could I be any better than this? (35 points): Defeat 300 enemies with The Missing Link.
Bull Rider (10 points): Destroy 10 Turrets using the Rodeo mode while climbing with The Missing Link.
Cowboy Master (20 points): Destroy 30 Turrets using the Rodeo mode while climbing with The Missing Link.
Strike with Attitude (10 points): Use The Missing Link's Leap Attack for the first time.
Expert Pitcher (10 points): Throw 25 enemies with The Missing Link.
Pinball Fan (10 points): Use the Bumpers for the first time.
Around the World (10 points): Use the Pole Vault for the first time.
Glutton (15 points): Swallow 20 enemies/objects with B.O.B.
Gourmet (30 points): Swallow 50 enemies/objects with B.O.B.
Machine Gun Specialist (20 points): Complete one B.O.B. Turret sequence without being hit.
Safety First (10 points): Activate B.O.B.'s Shield for the first time.
Olympic Champion (10 points): Get a medal for all Monster Challenges.
Gold Olympic Champion (30 points): Get a Gold Medal for all Monster Challenges.
My Thumb Hurts (20 points): Get a score of 5,000,000.
Be my Guest (50 points): Get a score of 10,000,000.

Additionally, there are six secret achievements:

Team Spirit (10 points): Complete Chapter 1 Without failing more than 10 times.
Team Victory (10 points): Complete Chapter 2 without failing more than 10 times.
Team Glory (25 points): Complete Chapter 3 without failing more than 10 times.
Team Supremacy (35 points): Complete Chapter 4 without failing more than 10 times.
Remember the Heroes (80 points): Complete the game without failing 10 times.
Defying Gravity (50 points): Jump 150 times with each monster.