anticlimax

nouns

a disappointing decline after a previous rise
"the anticlimax of a brilliant career"
anticlimax
is derived from
anticlimactic
is a type of (narrower)
a sudden decline in strength or number or importance
"the fall of the House of Hapsburg"
downfall, fall
a change from a serious subject to a disappointing one
anticlimax, bathos
is derived from
anticlimactic