Here is the full list of all 12 Worms achievements worth 200 gamerscore. It takes around 8-10 hours to unlock all of the achievements on Xbox 360.
Complete all 20 single player challenges
Inflict 20,000 damage
Collect 50 crates
Kill 100 enemy worms
Kill 15 worms using only Sheep
Trigger 25 Mines
Blow up 25 barrels
Inflict 2,000 damage
Kill 3 worms with one shot
Play a four player Xbox Live game
Inflict 500 damage
Complete training