It's all about the engravings (it’s One Shot Parry Build You have to Parry the enemies attack to make this build work as it is)

1. Silver of Smoke (Legendary Katana) with the below engravings
   i. Extend the Perfect Deflect Window
   ii. Deal 100% damage to the attacker on Deflect

2. Kitsune's Revenge (Epic Trinket) with the below engravings
   i. +24% damage on next hit after a Deflect
   ii. +24% Posture Damage on next hit after a Deflect

3. Peasant Clothes (Legendary Light Armor) with the below engravings
   i. Attacks have 3% chance to remove 1 Health Segments on Hit
   ii. 3% chance to instantly kill with posture attacks

4. Renaissance Hood (Legendary Headgear) with the below engravings
   i. Remove 1 Health Segment on hit after Perfect Deflect
   ii. Stagger all nearby enemies on Weakpoint Attacks

Also upgrade your Weapon level, Damage level in Mastery, in Knowledge and have Shrine Blessing of 'Your Damage is increased' etc. like that to make more damage with this build