In economic terms, an "index of downfall" refers to the point where growth stagnates and contraction begins.

The peak feels permanent. But the index of downfall is always there—quiet, precise, and unforgiving.

—stocks that have experienced the most significant percentage decline in a single trading session. Real-Time Tracking : Platforms like Moneycontrol

In the context of the internet, the term "Index of" refers to a server's directory listing. Users often search for "Index of Downfall" to find hosted files of: