Here is the full list of all 20 Shovel Knight: King of Cards achievements.
Beat the game within 1 hour and 30 minutes.
Finish New Game Plus.
Complete the game in fewer than 25 stages.
Finish the game without acquiring any heirlooms, health upgrades, or vigor upgrades. Armors are ok!
Clear all 4 houses of Joustus without buying or reclaiming cards from Chester. (Not in New Game+)
Obtain all Joustus cards.
Finish a Joustus Judge stage without dying or collecting any food or health hearts.
Find King Knight's secret room!
Finish a stage and jump fewer than 10 times.
Use each one of Chester's Cheat Cards.
Collect all Merit Medals.
Defeat every possible Joustus opponent.
Find and complete all stages and stage paths, and defeat all wandering travelers.
Acquire all armor, heirlooms, fancy things, and upgrades.
Commission a finished portrait!
Use only heirlooms to defeat any boss!
Clear all 4 houses of Joustus, and win the final battle...
Lose a unique card, then win it back!
Finish the game.
In a Joustus match with more than one gem, win by claiming every gem.