Here is the full list of all 20 Shovel Knight: Specter of Torment achievements.
Finish the game.
Find and return all Red Skulls.
Acquire all armor, curios, and upgrades.
Finish New Game Plus.
Finish the game without acquiring any Will or Darkness upgrades.
Finish any main stage without taking damage.
Beat the game within 1 hour and 30 minutes.
Destroy every possible checkpoint in the game.
Emerge unscathed from a battle with any boss besides Black Knight!
Obtain all Darkness and Will Upgrades from within the stages.
Reach the top of the climbing mini game.
Without replaying any stage or minigame, finish the game while holding 60000 gold or more.
Speak with every recruit within the Tower.
Chain together multiple targets with dash slashes 500 times.
Complete any Order of No Quarter recruit stage using your standing slash 10 times or fewer. Dash Slashes are ok!
Find Specter Knight's secret room!
Fill both of the tower's mysterious jars.
Land all 3 rail tricks in a single grind.
Use only curios to defeat any Boss Specter Knight is trying to recruit!
Reminisce and remain still on the Tower's rooftop for 30 seconds.