Lethal Strike and what is it?

What is lethal strike? is it a passive skill or something?

Leathal and passive don't really mix up imo...Isn't that one of the 76+ skills? I think enough Daggers of that high lvl can give you better info then I can.

no its lealth blow...but if you read the notes for c5 it says that lethal strike has been added to deadly blow, blinding blow and backstab

This what is says in the patch notes

21. Lethal Strike’s effect has been added to Deadly Blow and Blinding Blow.

22. The Lethal Strike and skill critical effects (skill damage x2) have been added to Backstab, and the damage of Soulshots has been increased due to a change in the damage formula.

23. A cancel target effect has been added to Stun Shot, Trick, and Switch.

24. A skill critical effect has been added to Double Shot (Skill damage x2).

20. Lethal Strike’s effect has been increased.

Effect 1: At a low probability, it lowers monsters’ HP by 50% and players’ CP to 1.
Effect 2: At an extremely low probability, it lowers monsters’ HP to 1 and players’ CP and HP to 1.