Here is the full list of all 18 Floppy Knights achievements.
Conquer all Challenge Levels
Acquire every card
Spend 1000 BigCoin in the Workshop
Complete all Objectives in Episode 7
Complete Squad Attack in a single turn
Complete all Objectives in Episode 6
Complete all Objectives in Episode 5
Complete Old Friends with Bernard at full HP
Complete a level with a deck of 30 cards
Complete Finals in Science Fair with a deck of 12 cards
Complete all Objectives in Episode 4
Unlock another new deck
Complete all Objectives in Episode 3
Complete all Objectives in Episode 2
Unlock a new deck
Complete Molten Mania with Bernard at full HP
Complete a level with just a Commander
Complete all Objectives in Episode 1