Here is the full list of all 20 Monster Girl Club Bifrost achievements.
Made 300 clients into happy campers
Had a girl with all stats exception affection at lv.7
Had a girl with all stats exception affection at lv.6
Used up 50000 of clients' energy
Made 100 clients into happy campers
Reached 500% customer satisfaction
Constructed everything in the same run
Maxed a construction
Cleared Normal Mode
Used banned badge on 3 rough clients
Made over 5 million G in the same run
Used banned badge on 3 hot guys
Reached 300% customer satisfaction
Made over 1 million G in the same run
Raised a queen
Fulfilled 20 escort requests
Owned 3 "Maid Knowledge" girls at once
Cleared Hard Mode
Cleared Expert Mode
Cleared Hard Mode without any new game plus bonus