Anticlimax
Part of speech: noun
Definition: A break in the final crescendo or climax of a narrative, producing a disappointing end.
Bathos
Part of speech: noun
Definition: Depth, bottom.An abrupt change in style, usually from high to low; an unintended transition of style; an anticlimax.Triteness; triviality; banality.Overly sentimental and exaggerated pathos.