an·ti·cli·max
/ˌænˌtaɪˈklaɪˌmæks/ noun plural an·ti·cli·max·es
: something that is much less exciting or dramatic than it was expected to be : a dull or disappointing ending or result [count] ▪ The last chapter of the book was an anticlimax. [noncount] ▪ The movie ended in anticlimax.
— an·ti·cli·mac·tic
/ˌænˌtaɪˌklaɪˈmæktɪk/ adjective
▪ The last chapter of the book was anticlimactic. ▪ The trial was anticlimactic, since it ended without a verdict.