Here is the full list of all 12 Swarm achievements worth 200 gamerscore. It takes around 15-20 hours to unlock all of the achievements on Xbox 360.
Kill 50 Swarmites
High scores add up to more than 1,000,000
Unlock 9 Death Medals
Replay levels 1, 2 and 3 after level 4 is unlocked
Achieve a 2X time bonus
Achieve a high score of 42,000,000
Light your multiplier on fire.
Kill the 1st boss
Kill the final boss
Collect all DNA
Reach a 70X multiplier
Unlock all Death Medals and turn all Progressive Death Medals to gold.