The thing in question can be a wounded animal or a dysfunctional relationship. In mild sense, it can be an object or idea that requires a lot of investment for it, and when it turns out that it not working you want to cut it down to avoid further loss.
Is there an idiom, proverb, or common saying that describes this situation?
Related: Is there an idiomatic way to say "go to the path of no way out"?
Best Answer
You can put the animal out of its misery. It means to euthanize.
I suppose you could say the same of a failing business enterprise, figuratively, and even of a dysfunctional relationship, when speaking with a sort of grim humor, where you're casting the relationship as a badly injured or terminally ill and suffering creature.