Here is the full list of all 55 Onimusha: Warlords achievements.
Obtain the Bishamon Sword.
Absorb souls from carp.
Enhance all swords to maximum.
Enhance the gauntlet to maximum.
Solve all decoder boxes.
Use Power Jewels to increase Vitality to maximum.
Complete the second half of the Dark Realm.
Complete the first half of the Dark Realm.
Win a power struggle with a demon.
Strike a demon with Kaede's Special Attack.
Unlock Samanosuke's alternate outfit.
Complete the game in less than 3 hours.
Defeat Fortinbras.
Collect all maps.
Defeat Marcellus's final form.
Open the gate to the Demon World.
Defeat Hecuba.
Solve all number puzzles.
Obtain all armor for Samanosuke.
Enhance all orbs to maximum.
Use the Decorated Sword to enter the East Area.
Obtain all long-range weapons.
Defeat Barabazuu.
Kill a demon with a battering ram.
Speak to the first and second old moth man.
Obtain the Vision Staff.
Defeat Stylado.
Obtain the Sacred Knife.
Cut down bamboo in the bamboo forest.
Obtain the Rosary of Communication.
Unseal the path to the Keep Underground.
Obtain the Arashi.
Defeat Marcellus.
Solve the crest puzzle.
Enter the abandoned keep.
Obtain the Kouen.
Defeat Osric.
Enhance equipment at Magic Mirror.
Save a soldier under attack by demons.
Use a Special Attack to kill a demon.
Obtain the Shiden.
Use the gauntlet to absorb demon souls.
Complete the game on Normal without enhancing swords or using Jewels.
Complete the game on Ultimate difficulty.
Complete the game on Normal without using herbs or medicine.
Complete the game and get an S Rank.
Complete all stages of Oni Spirits.
Collect all files.
Collect all Fluorite.
Unlock Kaede's alternate outfit.
NEW_ACHIEVEMENUse Magic Jewels to increase Magic Power to maximum._DESC_2_7
Strike Marcellus's final form with a Deflect Critical attack.
Defeat a demon by knocking it down the waterfall.
Spot the flock of wild geese at dusk.
Find the beetle on the tree trunk.