'At the end' is more specific. It describes the time at the end of some event or some series of events. "At the end of the day, we had supper." "There was one final ceremony at the end of the games." "In the end" usually describes some undefined period, describing what happens after. "In the end, we all must face death." - 'The end' here is the final analysis, some time which we can't escape. "In the end, it didn't really matter that we made a few mistakes." - After some event, when we look back, the mistakes didn't matter. The time when we look back is after the event, but not specified as to exactly when it happens.

Let me give you two good examples for further illustrations" 1.I saw him at the end of the party 2.In the end,I saw him at the party In the end means finally at the end indicates the last part of sth.Hope this helped!

You can see that difference in these examples: At the end: I left at the end of the film. In the end: We waited for ages, and in the end (finally) we left.