Used for the peak or most intense point of a story, event, or process, similar to English 'climax'.
映画のクライマックスで涙が出た。
I cried at the climax of the movie.
交渉はクライマックスを迎えた。
The negotiations reached a climax.
The drama reached its climax in the final episode.
The match reached its climax in the second half.
You can't watch the movie's climactic scene without crying.
クライマックス is typically used for the climax of a story, movie, or performance, while 盛り上がり is broader and can describe the excitement of any gathering or conversation.
クライマックス is another loanword focused narrowly on the emotional peak of a story, while ハイライト can cover multiple standout moments, not just one peak.
クライマックス refers to the peak of excitement or tension in a story, whereas フィナーレ specifically means the concluding segment that follows or embodies that peak.