"Dirt Nap! Bye bye!"
Silent Kill is X-23's very unique two part Level 3 Hyper Combo. X-23 becomes invisible for a short time, flickering slightly when struck by enemy attacks. While invisible she can perform an unblockable attack on her opponent, appearing above them and stabbing them in the back of the head by pressing the Special button when in close range.
Once activated, X-23 becomes invisible for 5 seconds. While invisible, everything fuctions normally except for the Special attack button.
Silent Kill is an unblockable attack (not a throw) that deals 400,000 points of damage, and can be done in the air. The best way to set up for this attack is to lockdown your opponent with assists or put them in a situation where they cannot escape. You can follow up the Silent Kill with an OTG Ankle Slice.