At the end v. in the end

At the end (of something) = at the time when something ends

• I’m going away at the end of March / at the end of the month.
• At the end of the game, people shouted.
• All the actors bowed at the end of the show.

You cannot say “in the end of something”.
So you cannot say “in the end of March” or “in the end of the show”.

The opposite of at the end is at the beginning
at the beginning of March
at the beginning of the show

In the end = finally

We use in the end when we say what the final result of a situation was.
• She giggled louder and louder. In the end she was laughing out loud.
• We kept arguing, and in the end we grew quite distant.
• We couldn’t decide where to go for holidays, so in the end we stayed home.

The opposite of in the end is usually at first
• At first I didn’t like reading, but in the end I couldn’t stay away from books.