Here is the full list of all 23 My Super Defender - there are Battle Santa Edition achievements.
Kill 200 enemies
Kill 200 enemies together with your friend
Kill 150 enemies together with your friend
Kill 150 enemies
Kill 75 enemies
Kill 100 enemies
Kill 100 enemies together with your friend
Kill 50 enemies
Kill 50 enemies together with your friend
Kill 25 enemies
Begin the level 12
Begin the level 11
Begin the level 10
Begin the level 8
Begin the level 9
Start the coop game with your friend on one PC
Begin the level 7
Begin the level 6
Begin the level 3
Begin the level 4
Begin the level 5
Begin the level 2
Begin the level 1