Anticlimactic (adjective)

Disappointingly less exciting or dramatic than expected.

Origin:

Late 19th century, from anti- (against) + climactic (related to a climax).

Examples:

1. The ending of the movie was anticlimactic.
2. The party was anticlimactic after all the build-up.
3. The anticlimactic reveal of the killer was a letdown for many viewers.
4. The anticlimactic finish to the match left the crowd disappointed.
5. The anticlimactic outcome of the election was not what the public expected.