Here is the full list of all 55 Onimusha: Warlords achievements.
Enhance the gauntlet to maximum.
Find the beetle on the tree trunk.
Spot the flock of wild geese at dusk.
Complete the game in less than 3 hours.
Defeat Fortinbras.
Defeat Marcellus's final form.
Strike Marcellus's final form with a Deflect Critical attack.
Open the gate to the Demon World.
Defeat Hecuba.
Use Power Jewels to increase Vitality to maximum.
Use the Decorated Sword to enter the East Area.
Kill a demon with a battering ram.
Complete the second half of the Dark Realm.
Complete the first half of the Dark Realm.
Defeat Stylado.
Obtain the Sacred Knife.
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.
Save a soldier under attack by demons.
Enhance equipment at Magic Mirror.
Obtain the Shiden.
Use the gauntlet to absorb demon souls.
Use a Special Attack to kill a demon.
Defeat Barabazuu.
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 all long-range weapons.
Obtain all armor for Samanosuke.
Obtain the Bishamon Sword.
Collect all files.
Collect all maps.
Collect all Fluorite.
Unlock Samanosuke's alternate outfit.
Unlock Kaede's alternate outfit.
Enhance all swords to maximum.
Enhance all orbs to maximum.
NEW_ACHIEVEMENUse Magic Jewels to increase Magic Power to maximum._DESC_2_7
Strike a demon with Kaede's Special Attack.
Defeat a demon by knocking it down the waterfall.
Win a power struggle with a demon.
Solve all number puzzles.
Solve all decoder boxes.
Absorb souls from carp.
Cut down bamboo in the bamboo forest.
Speak to the first and second old moth man.