You have probably been wondering what differentiates one phrase from the other. It is pretty simple.

‘In the end’ is an idiomatic expression that refers to the conclusion of something after a deliberation or uncertainty. It basically means ‘in conclusion’, ‘finally’, ‘in summary’, etc.

• In the end, we all die.
• The protagonist won in the end.
• In the end, there was no consensus.

‘At the end’ is a prepositional phrase that refers to the point when something stops—usually a single event.

• At the end of the seminar, the students filed out of the conference room.

The single event in the example above is the end of the seminar.

If ‘in the end’ is used, it would give the impression of a series of events, and not just one event.

• At the end of the service, the pastor bowed out.
• In the end, the pastor bows out.

NOTE: There is the idiom, ‘At the end of the day’, which is different from ‘at the end’. ‘At the end of the day’ also means ‘in the end’, ‘finally’, ‘in conclusion’, etc.