This idiom or expression refers to:

An accomplishment (or lack of it) that someone is famous for.

Her claim to fame is that she’s been nominated for an award eleven times without ever winning it!!!

This idiom or expression like phrase means:

One’s failure.
One’s cause of failure.

When someone says “The jail sentence was his undoing,” they mean something like “The jail sentence ruined his life.”

Another usage:
One’s own undoing.

When someone says “The jail sentence was his own undoing,” they mean “The jail sentence was his own fault.”

This idiom or expression means:

Failing in a big way.

A. This is where I met my Waterloo.
B. What happened?
A. I met you!!!

We learn by our mistakes.