Here is the full list of all 25 Witcheye achievements.
Clear Speedrun mode on Severe within 90 minutes
Beat the game on Severe
Clear Speedrun mode on Hard within 60 minutes
Clear Speedrun mode on Hard within 75 minutes, collecting everything
Clear the Boss Rush on any difficulty
Clear the Miniboss Rush on any difficulty
Beat the game on Hard with 100% collection
Beat the game on Hard
Use an enemy's minion against him
Defeat the final bosses without getting hit
Clear Speedrun mode on Normal within 45 minutes
Clear Speedrun mode on Normal within 60 minutes, collecting everything
Beat the game on Normal with 100% collection
Beat the game on Normal
Lead an adversary to his own undoing
Clear world 5
Defeat a sturdy opponent in an unexpected way
Transport a heavy explosive
Clear world 4
Take up the weapon of a defeated foe
Clear world 3
Be nice to someone who's minding his own business
Clear world 2
Clear world 1
Find a hidden treasure