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