When you have two options to chose between and either would not benefit you, so whichever you chose will be bad.
Like the word 'destined' with a more permanent bad destination.
Example:
It would make no difference to choose X over Y, they would both kill me. It was a (word)
Though not exactly a single word, consider the expression lose-lose situation (also known as no-win situation):
a situation in which a favorable outcome is impossible; you are bound to lose whatever you do
Your example:
It makes no difference to choose X over Y. They both will kill me. It's a lose-lose situation.
A whole phrase Between a rock and a hard place
In difficulty, faced with a choice between two unsatisfactory options.
Consider checkmate:
- (figuratively, by extension) Any losing situation with no escape; utter defeat.
It is still metaphorical, but a sentence about choices tend to go well with game metaphors.
Either choice would kill me. It was checkmate.
You don't specify, but if the scenario results from contradictory or paradoxical outcomes from either choice, you could call that a catch-22.
Derived from a 1960s novel of the same name, the canonical example of catch-22 is a scenario where a pilot that wants to fly more bombing missions in a war must be insane, and therefore should not be allowed to fly, but a pilot who says he is insane and should be excused demonstrates that he is rational, and therefore must fly the bombing mission.
I also like this quote from Nanny McPhee, which could be another example: When you need me but do not want me, then I must stay. When you want me but no longer need me, then I have to go. It's rather sad, really, but there it is.
I think a chess term that's better than checkmate is zugzwang (which sort of hit the "mainstream" when it was used on an episode of Criminal Minds):
[Oxford]
A situation in which the obligation to make a move in one's turn is a serious, often decisive, disadvantage.
‘black is in zugzwang’
‘After a while one would realise that this position looks like a mutual zugzwang’
The difference between this and checkmate is that the game isn't actually over; it's simply that you are forced into making a move that is bad for you—regardless of what that move is. (With checkmate, you can't actually move at all . . .)
...a losing proposition
or
...not a proposition
Unlikely to succeed; not a viable option.,
-Oxford Living Dictionary
Not a single word; I am not sure if there is a good one. But you could say,
"It would make no difference to choose X over Y, they would both kill me. It was a losing proposition/ not a proposition."
You say you want a “less metaphorical” term, so how about it was death either way
Colloquially, damned if you do, damned if you don't could work depending on context.
Predicament, quandary or dilemma. Though none of these indicate a complete no win situation.
If you want to avoid 'game over' because that phrase dates the dialog as being within the last 30 years or so, how about this:
It was curtains.
or to avoid a metaphor altogether while still conveying the starkness of the choices on offer, how about:
It was futile.
It was a fait accompli.
From Google:
fait ac·com·pli
/ˌfed əkämˈplē,ˌfād əkämˈplē/
noun
a thing that has already happened or been decided before those affected hear about it, leaving them with no option but to accept.
"the results were presented to shareholders as a fait accompli"
There are many expressions that could fill in that blank. One of the most literal is, no-win scenario.
If looking for a single word or phrase, death sentence seems like a just fit here.
It would make no difference to choose X over Y, they would both kill me. Either way, it was a death sentence.
Wiktionary defines death sentence as
(figuratively) Anything that spells death.
Eg: Having the Huntington's gene is a death sentence.
