i think those stats are awesome, they wold allow the spy to actually support his team, maybe the spy would gain a guarantied crit for each team-mate healed.

Crits are really useless on a knife that can insta-kill with a backstab. I think that the current stats are fine.

You could be able to crit with any weapon.

Pros
On backstab Poison (Like bleed with a Jarate visual)
+15 HP on wearer
+25% HP from Heath packs
Cons
Backstab does crit damage instead of insta kill

This looks good and I love the stats im all for it!

I like Panoϟ's stats but they seem a bit overpowered.

Pros:
Upon Backstab:Drains the enemies full health
Backstab on teammate after backstabbing an enemy :Heal your teammate for half the original HP of last back stabbed enemy.
Cons:
25% health on wearer
Blood held in the blood agent only stays good for 20 seconds and must be given to team mate before it expires.

The Pros :

on Backstab , Give U Speed Of The Same Speed When You Get Hit By The Disciplinary Action For 3 Seconds

---------------

The Cons :

Your Speed Will Be Like Demoman Speed , All The Time

The Cloake And Dagger Will Decreases So Fast While You On Speed

Balanced, new, and short statistics:

(!) Max HP of 175

Pros:
On backstab, you gain +25 max HP, (Up to 5 backstabs, +125 HP)
+15% Health from health sources

Cons:
-75 Max start-off HP (50HP)
-15% Ammunition from ammunition sources.

A good way for a spy to stay undetected before the enemy team knows a spy is around, then when they do know a spy is around, you are already buffed up and ready for getting in head-to-head combat when you have no other choice.

EDIT: Plus, the ammunition pickup con could be a good con since... you know.. your cloak...

What if it was like this:

First stab : fills the knife/needle
Second stab: releases it.
(so if the spy just stabs the air, the "charge" is lost.)

It's a thought I had randomly, but it might be a good con; ya'know? makes the player think about having to be aware and careful of the area and players around before healing a teammate.

I think healing is ryly good but -25% fs? Meybe -25% damage

Possible stats:

+ Apon backstab kill refills your health
- If the person being backstabbed is bleeding or on fire you become on fire or bleeding

Just so its not exactly like the kunai

you should be able to activate a small ubercharge or crit for a few seconds like kritzerg

Honestly I only see this as a Conniver's Kunai Reskin. I'll make a new thread on that though.

On Hit: Knife fills with blood
On Friendly Hit: Filled knife heals
On Backstab: Does not kill, causes bleed effect

pros
Backstab refills your health
Backstab gives +10% movement speed for 5 seconds

cons
Missing a backstab will cause you to bleed