You can win against a khan for his high sustain plus damage. If spotted get behind and create a crossfire to make him show his back to your team or to die from your poke.
This matchup is extremely difficult, but try to make her waste her fire by going planted, then immediately switching to travel form. (note that you will still take much damage but it won't be an insta kill)
Corvus stun is great counter to khan, as it passes through his shield and leaves him vulnerable for the kill. He's also an easy target to hit your knife.