ずじまい

1. 1Ended up never doing something one intended or had the opportunity to do, despite the chance.Ex. 1
2. 2With a potential verb, never managed to do something one wanted to, and the matter closed that way.Ex. 2
3. 3An expected or anticipated event ended up never occurring, whether or not anyone wanted it (e.g. 台風は結局上陸せずじまいだった).

Used when reflecting on a finished period or situation, such as a trip, a relationship, or a forecast period, in which an expected or hoped-for action or event never happened. The word 結局 often appears with it. The tone is often regretful, and it suits both conversation and writing. Unlike plain ずに, it marks the non-occurrence as the final outcome.

• 〜たきりN3〜たきり attaches to a verb's た form: the first action has already happened, and afterwards nothing follows or things simply stay in that state, possibly continuing up to the present. ずじまい, by contrast, means the very thing you wanted to do never got done in the end and the matter is closed, so the two generally cannot be swapped.
• ずに済むN2ずに済む also describes something not being done, but there the undone thing is a burden you wanted to avoid, and you feel relieved to have escaped it; ずじまい is for something you wanted to do, should have done, or had the chance to do that goes undone in the end, often with regret. The nuance differs, so they cannot be interchanged.
• あげくN2あげく attaches to a verb's た form or to a noun plus の: the first part is a long process, and the second part is the outcome it produces, usually an undesirable one. ずじまい attaches to a verb's ず form and means something never got done in the end, so the two cannot be directly swapped.
• てしまう / ちゃうN4ずじまい means something never got done in the end, while てしまう means you finished doing it or something irreversible happened; both can carry regret, but one is negative and the other affirmative, so they cannot be interchanged. ずじまい takes the ず form, てしまう takes the て form, and in casual speech てしまう becomes ちゃう.
• ずにN3ずに connects two actions within a sentence, meaning 'without doing...' or 'not doing... and...', and leans toward written style; ずじまい usually appears at the end of a sentence, stressing that the thing was never done in the end and the matter is closed. They attach in the same way, but they cannot be interchanged.

Unlike 〜たきり (an action was done, then the situation stayed unchanged), あげく (a bad result after a long process), and てしまう (regret over something that did happen), ずじまい stresses that an expected or intended action never happened at all. It also differs from ずに済む, which expresses relief at avoiding something, and from plain ずに, which simply means 'without doing'.