the hissing noise when behind an enemy is a bad idea.
if your trying to go for a "butter knife"/face stab play style then remember that the spy is very weak and relys on staying unseen to stay alive.

consider either a defence buff or only have it hissing when poised to back stab.

P.S; it's a snake, consider switching 2x damage for a poison effect; perhaps similar to bleed or maybe even a slowness to evedrything the victim does (fire rate,reload speed,movment speed, melee speed)

On Back stab it does poison damge for 8 seconds which takes 5 health and slows them down by 15% but does 25% less damage on a normal stab and if you miss slows you down becaus the snake bit you

pros
opponent 's screen is covered in ink for 6 seconds
30% faster weapon switch
cons
backstab does regular knife damage
25% damge penalty

pros

if you facestab them, they bleed/are poisined for 10-20 seconds
longer range than regular knife
people in an area have a chance of being poisined or/and their walk speed is 30% lower
30% faster walk speed


cons
upon backstab you have a chance of bleeding or to be poisined
take 30% more damage from all sources
has a chance to make a noise if you swing and miss or/and backstabing/facestabing them