Here is the full list of all 20 Tank Maniacs achievements.
Win a 1 vs 1 against a bot
Win a 1 vs 2 against bots
Win a 1 vs 3 against bots
Played 10 rounds
Played 100 rounds
Played 500 rounds
Opened 50 pickups
Opened 250 pickups
Opened 1000 pickups
Kill yo'self 100 times
Destroy 50 pickups
Try every single character
Try every single map
Get a triple kill
Win a match without killing anyone
Win an LMS match without losing a single life
Win a match without picking up any pickups
Let the autopilot win a match for you
Die in 10 seconds
Kill somebody while you are still on the parachute