Here is the full list of all 15 Operation KREEP achievements.
Killed 5000 "KREEP-lings".
Kill 1000 players!
Kill the KREEP when "KREEP eats people" and "CHAOS KREEP" mutators are set! "No sudden death" is not allowed...
Kill 9 "KREEP-lings" with your exploding corpse.
Kill two players with your exploding corpse!
Kill 5 players with 5 shots!
I used to think I was indecisive. Now, I'm not sure... Kill 10 players and 100 "KREEP-lings" in one match!
Kill yourself 100 times!
Tutorial completed.
Died during the tutorial.
Play a full match with all the mutators activated!
Try all mutators!
Kill two players with one bomb!
Kill two players with one rocket!
Play a match in which your shots never miss a "KREEP-ling" or a player.