I couldn't find a short idiom for a risky situation where you can either gain a lot, or lose a lot, but there is no in between.
In French, we use "quitte ou double", which was the name of a game where, at each successive question, either your gains were doubled, or you lost everything. It describes this well, but I doubt it still means something if translated word for word.
I was going to say "it's all or nothing" (As @Rathony said in the comments). But then I did some websearching. Read on.
"do or die", like "life or death" and "life and death", implies you could lose a lot, but doesn't imply that if you don't lose, you win. Only that you survive.
"high stakes" implies that you could win a lot or lose a lot. But it doesn't rule out the possibility that you could also break even or just win or lose just a little bit.
If you want to say "win a lot or lose a lot with nothing in between AND it is much more likely that you will lose than win", then you could go with "hail mary pass".
"double or nothing" exists, as does the less common "double or quits", but I don't think they have the same idiomatic usage as you attribute to "quitte ou double".
http://dictionnaire.reverso.net/francais-anglais/quitte%20or%20double/forced does suggest "double or quits" - in the sense of getting out of debt, or deeper into debt.
The same site also suggests "make or break", which I think is the best answer yet, because it has more of a hint or randomness and unpredictability than "all or nothing" does.
So I'll suggest "make or break".
An appropriate idiom is high stakes:
if you have high stakes in something such as a venture or decision, you have a major interest in its outcome
(Collins dictionary)
and it can also be used adjectivally:
- involving the possible loss of a large amount of money: a high-stakes poker game
- involving serious risks if there is no success: a high-stakes negotiation
- A high-stakes test is one that is very important for the person who takes it.
(Cambridge dictionary)
Arguably this fits the title ("Idiom for situation where you can either gain a lot or lose a lot") better than the body, as it doesn't so much convey the 'no inbetween' bit, but that might be obvious from the context (e.g. in a 'high-stakes test' with a pass/fail outcome).
There is "double or nothing." But you could perhaps also use "quitte ou double."
What comes to mind for me is high-risk/high-reward. I couldn't find an actual definition in any dictionary, but there are a lot of examples here:
http://www.linguee.com/english-french/search?source=auto&query=high-risk+high-reward
I've seen several other good answers on here, but I'll add this one as well since it's a more colloquial phrase:
And since I've seen a comment the OP put about waiting to see the result and possibly being in suspense of the outcome: "The die is cast" (Not that that particular one applies necessarily, but I like it anyway.)
Do or die is a common idiomatic expression used to convey the idea:
- said when you are in a situation in which you must take a big risk in order to avoid failure:
- On Tuesday, it's do or die in the final game.
Cambridge Dictionary
You could say "all in" -- this is the situation in poker where you bet all the chips you currently have, and therefore will either win the hand and stay in the game or lose everything and be out. This definitely has the sense of there being no in-between.
It can also imply that because you're in a risky situation where you could lose everything, that you're going to put the appropriate amount of effort in to ensure success. When Microsoft was entering the cloud services market, Steve Ballmer was known to say "we're all in in the cloud", which I always thought was a hilariously awkward sentence.
An expression I use for this, when bidding a rather dicky slam, or at other times, is "moon or bust". I can't find an exact reference for this, but the Urban Dictionary has a reference for or bust:-
or nothing
or die trying
An illustration of the point may be found here.
In such a situation you are playing a long ball game.
Refer SE question: What does "kick the long ball" mean?
Playing longball means to play for a few big pots with a few good hands instead of going for many, smaller pots with marginal hands, called smallball. The longball player waits for a good hand and then plays it aggressively, feeding pot early. https://www.pokerstrategy.com/glossary/Longball/
And for completeness, the opposite is a small-ball game.
Refer SE question: What does "Small-ball crap" mean?
Both these idioms are widely used in poker, sports and other fields to contrast high-risk but potentially lucrative strategies with more cautious strategies with lower potential gain.
the expression
in for a penny, in for a pound
suggests that you are already invested somewhat and now must either sacrifice your small investment or risk much more. it seems to capture the feel of "quitte ou double" only, in this case, it is "quit or multiply by 100". typically the expression is meant to suggest that you should increase your investment. if you want to discourage "doubling down", you would instead say "don't throw good money after bad"
side note: it's an old enough expression that it's original usages were in pre-victorian england. that means it originally meant "quit or multiply by 240". it also probably alluded to the fact that being in a debtor's prison was equally as unpleasant whether you were in the clink for failure to pay a penny or a pound.
There's one more expression you can use in this context, specifically when something is transitioning to more of a high stakes situation. In that case, you can say that
someone upped the ante.
The ante is the initial bet you have to put in the middle of the table in order to participate in that round. Literally, the phrase means that means that the dealer required that everyone put in a larger initial bet.
up the ante: to increase your risks or demands in order to get a greater advantage: The governor upped the ante in her war of words with the mayor, by calling him "dangerous" for the city.
Try the "64 thousand dollar question". This was a show where people answered questions and won prizes. The questions got more difficult and the prize was doubled each time. The contestant always had the choice to stop and keep the money won so far or continue and win double the previous amount. But if the contestant got it wrong all was lost. And the last possible amount was $64k.
There have been many more shows with the same idea but this was (one of) the first and the name stuck.
Mexican stand-off. Researched this situation to use within current WIP and this seemed to capture the essence of the situation. Confess the majority of my research is via Google.
Russian Roulette
A ‘do or die’ game of chance where the stakes are the player’s life - as one bullet loaded into the barrel of a gun is then randomly spun, and fired, at the player’s own head.
Example:
The relationship with Gelda felt more and more like ‘Russian Roulette’ - a desperate bid to win in a situation that was already spinning way out of control.
Buying the correct print cartridge in the sale felt like ‘Russian Roulette’ - commit - get the right one, print happily ever after - or die - with a plastic ill-shaped unusable cartridge forever rattling around the back of one’s desk.
https://www.collinsdictionary.com/dictionary/english/russian-roulette
A relevant idiom might be "boom or bust". I have heard it used a fair bit, especially in sporting contexts, drafting a player, and such. Often used in conjunction with the drafting of a certain player being considered a "gamble", and so forth.
Also gets used in other contexts, notably economics, though I don't believe in the kind of direct participatory sense that is being asked.
However, I do believe the sporting context fits.
"Putting all your eggs in one basket" - means the result will be a complete success or complete failure.
It could be argued that the gain/loss element is missing from this answer but it is easily implied.
Combining a couple of the above, in UK at least the most common phrase for this is a 'high stakes gamble'.
