anticlimax
/ˈæn.tiˌklaɪ.mæks/noun
High School
1
A failed or reverse climax, particularly
2
An unsatisfying resolution to a narrative, usually owing to a deus ex machina or similarly trivial resolution of the main conflict.
3
An abrupt descent (either deliberate or unintentional) from the dignity of the idea which the speaker or writer appeared to be aiming for.