anticlimacticadjective [ not gradable ]
us/ˌænt·i·klɑɪˈmæk·tɪk, ˌænˌtɑɪ-/causing unhappiness by being less exciting than expected or not as interesting as something that happened earlier:
The announcement of his resignation was anticlimactic, as we all knew he could no longer stay in the job.