Aký je rozdiel medzi „in the end“ a „at the end“?

2 answers
at the end = na konci
in the end = nakoniec
"at the end" can mean the end of a physical location or point of time. It can also refer to "at the end of the story" or " at the end of the day".

"in the end" is an idiom (common expression) in English. It usually means "in conclusion" or "finally" when speaking.