I mean, in other words:

Brutalising his/her opponent savagely with blunt weapon and combos until he's badly injuried should be an interesting new finishing move type.

But this move's real goal isn't killing your opponent.
For example, you could use your character special moves, a specific blunt weapon, and create your combos. The brutality will end when the opponent his too much damaged. (Example: the butality's goal could be breaking your opponent's leg and a bar shows the leg's health and when it's completely red you win)