あげく

あげく follows a verb in the た-form, or a noun with の, and says that a long or trying process ended badly: "after all that", "in the end". The kanji spelling is あげく挙げ句; kana is at least as common. It is at home in speech and in writing.

The first half has to be drawn out – repeated, prolonged or painful – and words like さんざん散々, なんど何度も or ながい長い often say so. A に after あげく changes nothing: なやんだ悩んだあげくに means the same as なやんだ悩んだあげく.

The second half is what already happened, so it is not a plan, a wish or a request.

• × よく考えたあげく、行ってください → よく考えてから、行ってください

あげく or 末に

すえに末に also means "after a long process", and its result can be good. あげく carries the speaker's regret or frustration, so a happy ending needs 末に.

• × 努力したあげく、合格した → 努力した末に、合格した

けっきょく結局 says "in the end" without either connotation. あげくのはてあげくの果てに adds the last and worst thing in a list of troubles: "and on top of all that".