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