Here is the full list of all 55 Onimusha: Warlords achievements.
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.
Defeat Stylado.
Defeat Barabazuu.
Obtain the Sacred Knife.
Use the Decorated Sword to enter the East Area.
Complete the first half of the Dark Realm.
Obtain all long-range weapons.
Obtain all armor for Samanosuke.
Enhance all orbs to maximum.
Use Power Jewels to increase Vitality to maximum.
Kill a demon with a battering ram.
Win a power struggle with a demon.
Cut down bamboo in the bamboo forest.
Speak to the first and second old moth man.
Strike a demon with Kaede's Special Attack.
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.
Obtain the Shiden.
Use the gauntlet to absorb demon souls.
Use a Special Attack to kill a demon.
Complete the second half of the Dark Realm.
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.
Obtain the Vision Staff.
Obtain the Bishamon Sword.
Collect all files.
Collect all Fluorite.
Unlock Samanosuke's alternate outfit.
Unlock Kaede's alternate outfit.
Enhance the gauntlet to maximum.
Enhance all swords to maximum.
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.
Solve all decoder boxes.
Spot the flock of wild geese at dusk.
Find the beetle on the tree trunk.
Absorb souls from carp.