What word means that every outcome is worse than where you started,
For example, You must make a choice but the choices are a worse situation than your current one.
This might be described as a "no-win situation"—a situation where there are multiple possible outcomes, but none of them are seen as positive.
A no-win situation, also called a “lose-lose situation”, is one where a person has choices, but no choice leads to a net gain.
Or from Dictionary.com:
A situation certain to end in failure or disappointment, as in If the in-laws visit them or they visit the in-laws, either way they see it as a no-win situation. [c. 1960]
You can use the word irresultive. It does not exactly mean, every outcome is a worse outcome, but it means, your outcome/result is furitless e.g. in chess, if you are facing a situation where, if you take any permitted permuted move, then those all probable moves will not yield any (favorable) results. So, normally you will say- "All moves are fruitless".
Merriam Webster dictionary defines irresultive as:
lacking result : ABORTIVE
Abortive according to Merriam Webster dictionary is,
Wordnik also backs irresultive as:
Useless or without result or done in vain.
Also, lose-lose is defined as adjective in oxford dictionary.
Of or denoting a situation which is disadvantageous or damaging to all those involved.
"Is it worth arguing in this lose-lose situation?"
A common idiom for this (at least in the case where you can see that one choice is not as bad as all the others) is least-worst:
the least worst choice is the best choice from a list of choices that you think are all bad
[Longman Dictionary of Contemporary English]