Here is the full list of all 16 Karl BOOM achievements.
Finish the Tutorial
Play 3 Quick Games to unlock the Survival Mode
Win a Quick Game
Hit another player in a Quick Game
Hit two players at once in a Quick Game
Hit three or more players at once in a Quick Game
Hit three or more bots at once in Survival Mode
Collect the maximum number of all Powerups
Win a Survival Mode game with bots set to easy difficulty
Win a Survival Mode game with bots set to normal difficulty
Win a Survival Mode game with bots set to hard difficulty
Survive insane difficulty - this is really really hard
Win 10 Quick Games
Win 50 Quick Games
Place 1,000 Bombs in Quick Games
Place 10,000 Bombs in Quick Games