Here is the full list of all 45 Blasphemous achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Unlock the ending A.
Get 100% of the game.
Achieve the maximum value of fervor.
Get all rosary beads.
Get all prayers.
Get all sword hearts.
Beat all the arena challenges.
Unlock the ending B.
Beat His Holiness Escribar.
Beat all types of enemies.
Discover all zones.
Beat Crisanta of the Anointed Blade.
Talk with all the corpses.
Release all cherubs.
Get all collectibles.
Visit the tomb of The Lady of the Tailed Gown.
Buy all the items of the Candelaria shops.
Achieve the maximum value of health.
Achieve the maximum value of rosary bead slots.
Bring all the offerings to the Blessed Lord of Salty Shores.
Get all relics.
Achieve the maximum value of flasks.
Help the Pilgrim reach his final destination.
Bring all the offerings to Lvdovico.
Help Cleofás in his path of redemption.
Buy all skills from the Mea Culpa shrines.
Achieve the maximum level of the Mea Culpa sword.
Beat Quirce, Returned by the Flames.
Beat Exposito, Scion of Abjuration.
Beat Melquíades, The Exhumed Archbishop.
Beat Esdras, of the Anointed Legion.
Witness the last moments of Viridiana.
Beat the Our Lady of the Charred Visage.
Hatch the Egg of Altasgracias.
Execute 5 different enemies.
Beat the Tres Angustias.
Kill 666 enemies.
Use the Righteous Riposte 5 times.
Beat Ten Piedad.
Beat the Warden of the Silent Sorrow.
Save all Kissers of Wounds.
Beat Perpetua.
Provoke the meeting between Redento and Cleofás.
Beat all bosses without flask consumption.
Cross the Bridge door in less than 3 hours.