IPA: /ˈdaʊn.fɔːl/
KK: /ˈdaʊnˌfɔl/
A sudden loss of power, wealth, or happiness, often leading to ruin or failure.
The politician's downfall was caused by a scandal that shocked the public.
Downfall is formed from "down" (from Old English "dūn", meaning down or lower) and "fall" (from Old English "feallan", meaning to fall). The word describes the act of falling down or a decline in status or fortune.
Think of something going 'down' and 'falling' — that's why downfall means a decline or a fall from a higher position.