It's going aggro? It's a "fuck up you got a lot of possibility to avoid this, you are dead (but take a debility if you want)" situation? Is something else?
You've got to remember, this is describing a PC vs PC conflict, which is different from dealing with NPCs... with NPCs, the MC is looking through crosshairs at them and if they "should" die... they
die! No one is going to complain... except their pissed off lover or some shit... *LAUGH*
With PCs, it's entirely different, you're attempting to deny the other player the use of their
character, and that's not something easy to do in this game. First off, in this situation, the MC should probably ask the defeated character, "Do you want to keep playing Snake Eyes, or are you cool with him dying here?" If the player is cool with that, then he dies, and everyone moves on.
If the player is
not cool with it, then the rules take over, and I'll refer specifically to the the Debilities section of the rulebook, page 165: the example there is a helpless, unconscious PC taking a shotgun blast to the
head!... it's not even a PC move, per se, it just happens, but the player on the receiving end still has some choice.