Complete each of the following achievements below to get the allotted gamerscore.

There are 12 achievements worth 200 points total.

Unlockables

Baiter Bane (20) During an Xbox Live Co-op game, kill 5 baiters in any level without using any smart bombs.

Competitive (15) Win 30 Xbox Live versus games.
Cooperation (10) Achieve a score of 15,000 during an Xbox Live CO-OP game.

Fifteen Grand (15) Obtain a personal score of 15,000.
Five Waves (20) Make it to the 5th wave.

Getting Better (15) Make it to the 3rd wave.

Mutant (10) Shoot 5 mutants in one game.

Nice Catch (15) Rescue a human with a mid-air catch.

One Wave (10) Make it to the 2nd wave without losing any humans.

Protect All Humans (25) Lose no humans in the first 3 waves.

Run! (20) Survive the first 75 seconds without shooting, bombing, or teleporting.

Twenty-Five Grand (25) Obtain a personal score of 25,000.