The Final Strike is a last ditch effort to strike down an enemy. It involves all the energies the witch or wizard has or has access to in order to deliver what is expected to be a killing blow. This would include pulling from key lines and/or nodes which may account for the sheer destructive power of this spell. A Final Strike also tends to result in the death of he or she who calls the Strike.
Known wizards and witches who have used Final Strike
Roderick Nolan Prince against Voldemort (Betrayer's Blade)