noun

The word "anticlimax" means a disappointing or underwhelming end or outcome to an expected event or situation, often resulting in a loss of excitement or a sense of deflation. It can also refer to a sudden drop in excitement or tension after a build-up or a situation where an expected event turns out to be less important or valuable than originally thought.

example

1. The long-awaited party ended with an anticlimax.
2. After all the excitement, the game ended with an anticlimax.
3. We were all expecting a surprise, but it ended with an anticlimax.