What differences are there between "at the end" and "in the end"?

‘At the end’ can refer to the end of a physical location, like ‘at the end of our hallway’. It can also be used to represent the closing or near completion of something, like ‘at the end of the story’ or ‘at the end of the film’. And, it can also mean the end point of a period in time;  ‘The score was nil nil at the end of the game.’  ‘I am going to go away at the end of the month.’

‘In the end’ means ‘finally’. ‘We all wanted to go to different places, in the end, we agreed to go to the beach.’  ‘We waited for the bus for 2 hours, in the end, we caught a taxi.’

From : http://www.learnersdictionary.com In the end / at the end Tuesday December 6th 2011 Question In the end / at the end Answer

Isaac, from Israel, asked about the difference between in the end and at the end, and when to use them.

In the end

In the end is used mostly as an idiom that means "finally," "after a long time," or, "when everything is considered." It is often followed by a comma. Here are some sentences with this idiom:

We worked hard, and in the end, we achieved our goal.
In the end, what really matters in a friendship is trust.

At the end

At the end is used in the idiom "at the end of the day." which means something similar to in the end (= when everything is considered). However, at the end is most commonly used more literally, as a prepositional phrase followed by of, to refer to the end of a specific noun. This noun can be a physical object, a period of time, an event, a place, or something more abstract, such as one's patience.

Here are some sentences with "at the end + of":

At the end of his life, he had no regrets.
Put a period at the end of every sentence.
I pay the phone bill at the end of each month.
There is a brick building at the end of the driveway.

In the end: a point in time (temporal) representing the final status of a situation, event, or some happening.

At the end: a point within physical space representing the position or situation of something; it may not have anything to do with finality.

In the end is often used to signify that something has occurred after consideration of various options and a period of uncertainty. So, ...

We looked at several pianos. They all had attributes we liked but in the end it was the small size of the upright that we went for.

At the end is usually used simply to specify a moment in time. So, ...

At the end of the game players add up how much money they each have and the winner is the person with the least (!)